Devices For Treating The Spine

ABSTRACT

Method and apparatus are disclosed for distracting tissue and particularly spinal tissue. The device and method may include insertion of at least one elongated member and an augmenting member to form a structure between the tissues to be distraction, such that a dimensional aspect of the structure is augmented upon movement of the augmenting structure.

The present application is a continuation-in-part of U.S. patentapplication Ser. No. 11/464,782, a continuation-in-part of U.S. patentapplication Ser. No. 11/464,790, a continuation-in-part of U.S. patentapplication Ser. No. 11/464,793, a continuation-in-part of U.S. patentapplication Ser. No. 11/464,807, a continuation-in-part of U.S. patentapplication Ser. No. 11/464,812 and a continuation-in-part of U.S.patent application Ser. No. 11/464,815, all of which were filed on Aug.15, 2006, and claim the benefit of U.S. Provisional Application No.60/708,691, filed Aug. 16, 2005, U.S. Provisional Application No.60/738,432, filed Nov. 21, 2005 and U.S. Provisional Application No.60/784,185, filed Mar. 21, 2006, all of the above are incorporatedherein by reference. In addition to claiming the benefit of the filingdates of all of the above regular and provisional applications, thepresent application also claims the benefit of U.S. Provisional PatentApplication No. 60/890,868, filed Feb. 21, 2007, and U.S. ProvisionalPatent Application No. 60/936,974, filed Jun. 22, 2007, all of which areincorporated herein by reference.

FIELD OF THE INVENTION

The present invention generally relates to apparatus and methodsemployed in minimally invasive surgical procedures and more particularlyto various aspects of apparatus and methods for separating and/orsupporting tissue layers, especially in the spine.

BACKGROUND OF THE INVENTION

A variety of physical conditions involve two tissue surfaces that, fordiagnosis or treatment of the condition, need to be separated ordistracted or maintained in a separated condition from one another andthen supported in a spaced-apart relationship. Such separation ordistraction may be to gain exposure to selected tissue structures, toapply a therapeutic pressure to selected tissues, to return orreposition tissue structures to a more normal or original anatomicposition and form, to deliver a drug or growth factor, to alter,influence or deter further growth of select tissues or to carry outother diagnostic or therapeutic procedures. Depending on the conditionbeing treated, the tissue surfaces may be opposed or contiguous and maybe bone, skin, soft tissue, or a combination thereof.

One location of the body where tissue separation is useful as acorrective treatment is in the spinal column. Developmentalirregularities, trauma, tumors, stress and degenerative wear can causedefects in the spinal column for which surgical intervention isnecessary. Some of the more common defects of the spinal column includevertebral compression fractures, degeneration or disruption of anintervertebral disc and intervertebral disc herniation. These and otherpathologies of the spine are often treated with implants that canrestore vertebral column height, immobilize or fuse adjacent vertebralbones, or function to provide flexibility and restore natural movementof the spinal column. Accordingly, different defects in the spinalcolumn require different types of treatment, and the location andanatomy of the spine that requires corrective surgical proceduresdetermines whether an immobilizing implantable device or a flexibleimplantable device is used for such treatment.

In a typical spinal corrective procedure involving distraction of tissuelayers, damaged spinal tissue is removed or relocated prior todistraction. After the damaged tissue has been removed or relocated,adjacent spinal tissue layers, such as adjacent bone structures, arethen distracted to separate and restore the proper distance between theadjacent tissue layers. Once the tissue layers have been separated bythe proper distance, an immobilizing or flexible device, depending onthe desired treatment, is implanted between the tissue layers. In thepast, the implantable treatment devices have been relatively largecage-like devices that require invasive surgical techniques whichrequire relative large incisions into the human spine. Such invasivesurgical techniques often disrupt and disturb tissue surrounding thesurgical site to the detriment of the patient.

Therefore, there remains a need for implantable treatment devices andmethods that utilize minimally invasive procedures.

Such methods and devices may be particularly needed in the area ofintervertebral or disc treatment. The intervertebral disc is dividedinto two distinct regions: the nucleus pulposus and the annulusfibrosus. The nucleus lies at the center of the disc and is surroundedand contained by the annulus. The annulus contains collagen fibers thatform concentric lamellae that surround the nucleus and insert into theendplates of the adjacent vertebral bodies to form a reinforcedstructure. Cartilaginous endplates are located at the interface betweenthe disc and the adjacent vertebral bodies.

The intervertebral disc is the largest avascular structure in the body.The cells of the disc receive nutrients and expel waste by diffusionthrough the adjacent vascularized endplates. The hygroscopic nature ofthe proteoglycan matrix secreted by cells of the nucleus operates togenerate high intra-nuclear pressure. As the water content in the discincreases, the intra-nuclear pressure increases and the nucleus swellsto increase the height of the disc. This swelling places the fibers ofthe annulus in tension. A normal disc has a height of about 10-15 mm.

There are many causes of disruption or degeneration of theintervertebral disc that can be generally categorized as mechanical,genetic and biochemical. Mechanical damage includes herniation in whicha portion of the nucleus pulposus projects through a fissure or tear inthe annulus fibrosus. Genetic and biochemical causes can result inchanges in the extracellular matrix pattern of the disc and a decreasein biosynthesis of extracellular matrix components by the cells of thedisc. Degeneration is a progressive process that usually begins with adecrease in the ability of the extracellular matrix in the centralnucleus pulposus to bind water due to reduced proteoglycan content. Witha loss of water content, the nucleus becomes desiccated resulting in adecrease in internal disc hydraulic pressure, and ultimately to a lossof disc height. This loss of disc height can cause the annulus to bucklewith non-tensile loading and the annular lamellae to delaminate,resulting in annular fissures. Herniation may then occur as ruptureleads to protrusion of the nucleus.

Proper disc height is necessary to ensure proper functionality of theintervertebral disc and spinal column. The disc serves severalfunctions, although its primary function is to facilitate mobility ofthe spine. In addition, the disc provides for load bearing, loadtransfer and shock absorption between vertebral levels. The weight ofthe person generates a compressive load on the discs, but this load isnot uniform during typical bending movements. During forward flexion,the posterior annular fibers are stretched while the anterior fibers arecompressed. In addition, a translocation of the nucleus occurs as thecenter of gravity of the nucleus shifts away from the center and towardsthe extended side.

Changes in disc height can have both local and global effects. On thelocal (or cellular, level) decreased disc height results in increasedpressure in the nucleus, which can lead to a decrease in cell matrixsynthesis and an increase in cell necrosis and apoptosis. In addition,increases in intra-discal pressure create an unfavorable environment forfluid transfer into the disc, which can cause a further decrease in discheight.

Decreased disc height also results in significant changes in the globalmechanical stability of the spine. With decreasing height of the disc,the facet joints bear increasing loads and may undergo hypertrophy anddegeneration, and may even act as a source of pain over time. Decreasedstiffness of the spinal column and increased range of motion resultingfrom loss of disc height can lead to further instability of the spine,as well as back pain.

Radicular pain may result from a decrease in foraminal volume caused bydecreased disc height. Specifically, as disc height decreases, thevolume of the foraminal canal, through which the spinal nerve rootspass, decreases. This decrease may lead to spinal nerve impingement,with associated radiating pain and dysfunction

Finally, adjacent segment loading increases as the disc height decreasesat a given level. The discs that must bear additional loading are nowsusceptible to accelerated degeneration and compromise, which mayeventually propagate along the destabilized spinal column.

In spite of all of these detriments that accompany decreases in discheight, where the change in disc height is gradual many of the illeffects may be “tolerable” to the spine and patient and may allow timefor the spinal system to adapt to the gradual changes. However, thesudden decrease in disc volume caused by the surgical removal of thedisc or disc nucleus may increase the local and global problems notedabove.

Many disc defects are treated through a surgical procedure, such as adiscectomy in which the nucleus pulposus material is removed. During atotal discectomy, a substantial amount (and usually all) of the volumeof the nucleus pulposus is removed and immediate loss of disc height andvolume can result. Even with a partial discectomy, loss of disc heightcan ensue. Discectomy alone is the most common spinal surgicaltreatment, frequently used to treat radicular pain resulting from nerveimpingement by disc bulge or disc fragments contacting the spinal neuralstructures.

The discectomy may be followed by an implant procedure in which aprosthesis is introduced into the cavity left in the disc space when thenucleus material is removed. Thus far, the most common prosthesis is amechanical device or a “cage” that is sized to restore the proper discheight and is configured for fixation between adjacent vertebrae. Thesemechanical solutions take on a variety of forms, including solidkidney-shaped implants, hollow blocks filled with bone growth material,push-in implants and threaded cylindrical cages.

A challenge in the use of a posterior procedure to install spinalprosthesis devices is that a device large enough to contact the endplates and expand the space between the end plates of the same oradjacent vertebra must be inserted through a limited space. In the caseof procedures to increasing intervertebral spacing, the difficulties arefurther increased by the presence of posterior osteophytes, which maycause “fish mouthing” or concavity of the posterior end plates andresult in very limited access to the disc. A further challenge indegenerative disc spaces is the tendency of the disc space to assume alenticular shape, which requires a relatively larger implant than oftenis easily introduced without causing trauma to the nerve roots. The sizeof rigid devices that may safely be introduced into the disc space isthereby limited.

While cages of the prior art have been generally successful in promotingfusion and approximating proper disc height, typically these cages havebeen inserted from the posterior approach, and are therefore limited insize by the interval between the nerve roots. Further, it is generallydifficult, if not impossible to implant from the posterior approach acage that accounts for the natural lordotic curve of the lumber spine.

It is desirable to reduce potential trauma to the nerve roots and yetstill allow restoration or maintenance of disc space height inprocedures involving vertebrae fusion devices and disc replacement,containment of the nucleus of the disc or prevention of herniation ofthe nucleus of the disc. In general minimally invasive surgicaltechniques reduce surgical trauma, blood loss and pain. However, despitethe use of minimally invasive techniques, the implantation of cagedevices for treating the spine typically involves nerve root retraction,an inherently high risk procedure. It is therefore desirable to reducethe degree of invasiveness of the surgical procedures required toimplant the device, which may also serve to permit reduction in thepain, trauma, and blood loss as well as the avoidance and/or reductionof the nerve root retraction.

In minimally invasive procedures, to monitor placement, it is usefulthat implant devices inserted into spinal tissue be detectable usingfluoroscopic imaging systems. However if a device is visible using X-raytechnology, then the device can interfere with the detection andmonitoring of spinal tissues, such as bone growing into the disc spaceafter a vertebral fusion procedure. Additional advances would also beuseful in this area.

SUMMARY OF INVENTION

The present invention relates to various aspects of distraction systemsand methods for separating, supporting or both separating and supportingtissue layers in the human body.

The present invention, in one aspect, is directed to a tissuedistraction device comprising a first elongated member insertablebetween tissue layers and adapted to define a structure in situ having adimensional aspect in a direction extending between the tissue layers.The device also includes an augmenting elongated member operativelycooperative with the first member to increase the dimensional aspect ofthe structure in situ.

In another aspect, a tissue distraction device is provided by thepresent invention comprising a first elongated member, a secondelongated member, and an augmenting elongated member, with the firstelongated member adjacent the second elongated member. The first andsecond elongated members are insertable between tissue layers to definea structure in situ having a dimensional aspect in a direction extendingbetween the tissue layers. An augmenting elongated member is operativelycooperative with the first and second members to increase thedimensional aspect of the structure in situ.

In accordance with another aspect of the invention a method is providedfor separating tissue layers. The method includes inserting a firstelongated member between tissue layers to form a structure in situ witha dimensional aspect in a direction extending between the tissue layers.The method further includes inserting an augmenting elongated memberbetween tissue layers, the augmenting elongated member cooperating withthe first member to increase the dimensional aspect of the structure insitu and to cause spreading of the tissue layers.

In accordance with yet a further aspect of the present invention amethod of separating tissue layers is provided that comprises insertingfirst and second elongated members. The method includes inserting firstelongated member and the second elongated member between tissue layersto form a structure in situ with a dimensional aspect in a directionextending between the tissue layers. The method further includesinserting and augmenting elongated member between tissue layers theaugmenting elongated member cooperating with the first and secondelongated members to increase the dimensional aspect of the structure insitu and to cause spreading of the tissue layers.

These and other aspects of the present invention are set forth in thefollowing detailed description. In that respect, it should be noted thatthe present invention includes a number of different aspects which mayhave utility alone and/or in combination with other aspects.Accordingly, the above summary is not exhaustive identification of eachsuch aspect that is now or may hereafter be claimed, but represents onlyan overview to assist in understanding the more detailed descriptionthat follows. The scope of the invention is as set forth in the claimsnow or hereafter filed.

BRIEF DESCRIPTION OF THE FIGURES

In the course of this description, reference will be made to theaccompanying drawings, wherein:

FIG. 1 is a perspective view of one embodiment of a distraction devicesupport structure defined by a first elongated member that has acoil-like or a spring configuration;

FIG. 2 is a perspective view of the distraction device support structureof FIG. 1 augmented by an augmenting elongated member positioned betweenthe windings of the first elongated member;

FIG. 3 is a perspective view of a vertebra having a guide memberdeployed therein;

FIG. 4 is a perspective view of the vertebra of FIG. 3 to show a firstelongated member partially deployed within the vertebral body;

FIG. 5 is a perspective view of the vertebra of FIG. 3 shown with thefirst elongated member fully deployed to define a support structurewithin the vertebral body;

FIG. 6 is a perspective view of the vertebra of FIG. 3 having portionsbroken away to show an augmenting elongated member being initiallydeployed between the windings of the first elongated member;

FIG. 7 is a perspective view of a vertebral body having portions brokenaway to show the deployment of an augmenting elongated member to augmentthe distraction device support structure;

FIG. 8 is a perspective view of a vertebral body having portions brokenaway to show the augmented distraction device support structureimplanted therein;

FIG. 9 is a partial cross-sectional view of a distraction device supportstructure prior to deployment of the augmenting elongated member;

FIG. 10 is a partial cross-sectional view of the distraction devicesupport structure of FIG. 9 shown with the augmenting elongated memberpartially deployed;

FIG. 11 is a partial cross-sectional view of the distraction devicesupport structure of FIG. 9 shown with the augmenting elongated memberfully deployed;

FIG. 12 is a perspective view of another embodiment of a distractiondevice support structure defined by a first elongated member and anaugmenting elongated member;

FIG. 13 is a partial cross-sectional view of the distraction devicesupport structure of FIG. 12 to show the augmenting and first elongatedmembers;

FIG. 14 is a perspective view of another embodiment of a distractiondevice support structure defined by a first elongated member and anaugmenting elongated member;

FIG. 15 is a partial cross-sectional view of the distraction devicesupport structure of FIG. 14 illustrating a stress relief region in thefirst elongated member;

FIG. 16 is a perspective view of a distraction device with firstelongated member having expandable walls or variable height;

FIG. 17 is a perspective view of a portion of the first elongated memberof the distraction device of FIG. 16;

FIG. 18 is a perspective view of a portion of the augmenting elongatedmember of the distraction device of FIG. 16;

FIG. 19 is a perspective view of the augmenting elongated memberoperatively cooperating with the first elongated member of FIG. 16;

FIG. 20 is a perspective view of a vertebral disc having portions brokenaway to show the first elongated member of FIG. 16 deployed therein toform a structure in situ having a dimensional aspect in a directionbetween extending tissue layers (end plates of the disc);

FIG. 21 is a perspective view of the vertebral disc of FIG. 20 havingportions broken away to show the augmenting elongated member beingdeployed within the first elongated member to augment or increase thedimensional aspect of the distraction device support structure;

FIG. 22 is a perspective view of a semicircular distraction devicehaving a first elongated member, a second elongated member and anaugmenting elongated member forming a structure as it would appear insitu in a disc or vertebra;

FIG. 23 is a top view of another embodiment a distraction device supportstructure with a protrusion on the distal end of the device interactingwith a recess near the distal end of the device;

FIG. 24a is a top view of a elongated member of a distraction devicehaving spaced-apart teeth and intermediate slots;

FIG. 24b is a top view of an elongated member of a distraction devicehaving spaced-apart teeth and slots as well as a protrusion at thedistal end and a notch or recess near the proximal end of thedistraction device that could form into the structure in situ as shownin situ as shown in FIG. 23;

FIG. 25 is a perspective view of an augmenting elongated member of adistraction device having first conformation of spaced-apart teeth andslots along one side and a second conformation on a second side toaccommodate bending in one direction and resisting bending in anopposite direction;

FIG. 26 is a perspective view of a vertebral disc having portions brokenaway to show the first and second elongated members of the distractiondevice of FIG. 22 deployed in a vertebral disc and the augmentingelongated member in a delivery cannula;

FIG. 27 is a perspective view of a vertebral disc having portions brokenaway to show the use of a cannula to deploy the augmenting elongatedmember in a vertebral disc between the first and second elongatedmembers to augment the support structure of the device;

FIG. 28 is a perspective view of a vertebral disc between two vertebrahaving portions broken away to show an augmenting elongated member fullydeployed between the first and second elongated members in a vertebraldisc causing the first and second elongated members to contact anddistract the vertebra above and below the disc;

FIG. 29 is a side view of portions of a distraction device showing atapered distal end of an augmenting elongated member approaching theproximal end of the first and second elongated members of the device;

FIG. 30 is a perspective view of portions showing the tapered distal endof an augmenting elongated member entering a ramped opening formed bythe proximal ends of first and second elongated members;

FIG. 31 is an proximal end-view of first and second elongated members ofa distraction device, showing wire lumens, tissue engaging protrusions,and elongated grooves with ramped entry as employed in FIG. 30;

FIG. 32 is an end-view of another embodiment of an augmenting elongatedmember of a distraction device with protrusions on top and bottomsurfaces;

FIG. 33 is an end-view of a deployed augmenting elongated member withbulbous ends on its raised ribs interacting with the elongated groovesof the first and second elongated members as employed in FIG. 30;

FIG. 34 is an end-view of a deployed augmenting elongated member with araised rib interacting with a groove in a first elongated member and agroove in the augmenting elongated member interacting with a raised ribof a second elongated member;

FIG. 35 is a perspective view of first and second elongated members of adistraction device emerging from a cannula with cutouts on the top andbottom distal end of cannula;

FIG. 36 is an end view of first and second elongated members of adistraction device when located in a cannula;

FIG. 37 is an exploded side view of a delivery device showing athumbknob and a puller platform to control the tension on pull wires,plunger body, inner delivery cannula, and outer syringe body with maindelivery cannula;

FIG. 38 is side view the assembled delivery device of FIG. 37 with thepull wire ferrule attaching a pull wire to the puller platform;

FIG. 39 is a perspective view of the pull wire system and the first andsecond elongated members with tension on the pull wires causingcurvature of the elongated members emerging from the cannula;

FIG. 40. is a top view of the pull wire system and the first and secondelongated members of FIG. 39 with tension on the pull wires causingcurvature of the elongated members emerging from a cannula;

FIG. 41. is a top view of the pull wire system and the first and secondelongated members of FIG. 39 with an increased tension on the pull wirescausing increased curvature of the elongated members emerging from acannula;

FIG. 42. is a perspective view of an augmenting elongated member havinga recess in its proximal end which interacts with a delivery deviceplunger;

FIG. 43 are a perspective views of delivery device with anchor loops toattach elongated members;

FIG. 44 is a perspective view of a distraction device with curvaturecontrolled by pull wires and attached to a delivery device by anchorloops;

FIG. 45 is a top view of a distraction device deployed in a disc andlocated adjacent or against the annulus of a disc with a cannuladelivering bone graft material.

FIG. 46 is a top view of a distraction device deployed in a disc againstthe annulus of a disc with bone graft material filling much of the discspace including an access opening or aperture in the annulus of thedisc;

FIG. 47 is a perspective view of a guide wire delivery system with firstsecond and augmenting elongated members loaded on the guide wire in acannula;

FIG. 48 is a perspective view of the distraction device of FIG. 47 withthe augmenting elongated member deployed using a guide wire between thefirst and second elongated members, for clarity the distraction deviceis shown as straight, although it is preferably in a curvedconfiguration in situ;

FIG. 49 is a longitudinal cross-section of a distraction device withprotrusions or threads on the augmenting elongated member interactingwith protrusions on the bottom surface of the first elongated member andthe top surface of a second elongated member;

FIGS. 50, 51, 52 and 53 are end views of examples of the proximal endsof the augmenting elongated members configured to interact with torquedelivery devices;

FIG. 54 is a top view of a segmented augmenting member loaded on adelivery wire;

FIGS. 55-60 are views of examples of alternative segments of segmentedaugmenting members, FIGS. 55, 56, 58, 59 and 60 are top views ofsegments and FIG. 57 is a perspective view of a segment;

FIG. 61 is a perspective view of a distraction device with radiopaquemarkers in the augmenting, first and second elongated members;

FIG. 62 is a perspective view of an augmenting elongated member with apin extending above the top and bottom surfaces thereof to provide aprotrusion useful as an interlocking feature to interlock with the firstand/or second elongated members;

FIG. 63 is a perspective view of an elongated member with a recessextending that acts as an interlocking feature to receive the pin of theaugmenting elongated member of FIG. 62;

FIGS. 64 and 65 are perspective views of examples of pin-typeinterlocking features;

FIG. 66 is a cross sectional view of a proximal end of distractiondevice with the interlocking features of the augmenting, first andsecond elongated members unengaged;

FIG. 67 is a cross sectional view of a proximal end of distractiondevice with the interlocking feature of the augmenting, first and secondelongated members engaged;

FIG. 68 is a side view of an elongated augmented member with recesses toprovide interlocking features;

FIG. 69 is side view of a distraction device having spaced apart teethor spreading members on a first lateral side with the augmentingelongated member in a first position between the first and secondelongated members;

FIG. 70 is a side view of the other side of the distraction device ofFIG. 69 lacking spaced apart teeth, and with the augmenting elongatedmember in a first position between the first and second elongatedmembers;

FIG. 71 is a side view of the distraction device of FIG. 69 with theaugmenting elongated member in a second position between the first andsecond elongated members spreading the first and second members apart toincrease their dimensional aspect;

FIG. 72 is a perspective view of distraction device having spaced apartteeth or spreading members on a first lateral side with the augmentingelongated member in a first position between the first and secondelongated members;

FIG. 73 is a perspective view of the distraction device shown in FIG. 72with the augmenting elongated member in a second position between thefirst and second elongated members spreading the first and secondmembers apart to increase their dimensional aspect;

FIG. 74 is a perspective view of the augmenting elongated member of thedistraction device shown in FIG. 72;

FIG. 75 perspective view of the distraction device shown FIG. 72 in acurved configuration as it may be configured in situ, with theaugmenting elongated member in a first position between the first andsecond elongated members, the device having a dimensional aspect (e.g.,the distance between the upper and lower surfaces of the device) thatextends in a direction between two facing tissue layers (not shown) whenin situ;

FIG. 76 perspective view of the distraction device shown FIG. 72 in acurved configuration as it may be configured in situ with the augmentingelongated member in a second position between the first and secondelongated members spreading the first and second members apart andincreasing the dimensional aspect of the structure to result indistraction of tissue layers in situ;

FIG. 77 is a perspective view of a distraction device of the presentinvention shown in a first configuration; and

FIG. 78 is a perspective view of a distraction device of FIG. 77 shownin an augmented configuration.

DETAILED DESCRIPTION

The devices and methods of the present invention provide multiplefeatures of distraction devices, distraction device support structuresand deployment systems that can be used to actively separate tissuelayers by engaging them and forcing them apart, or to support theseparation of tissue layers separated by the distraction device itselfor by other devices or processes or a combination of these.

As used herein, the terms “distraction device” and “distraction devicesupport structure” are intended to have a general meaning and is notlimited to devices that only actively separate tissue layers, onlysupport tissue layers or only both actively separate and support tissuelayers. For example, the distraction device and support structure ingeneral can be used to actively separate layers of tissue and then beremoved after such separation, or the distraction device and the supportstructure could be used to support layers of tissue that have beenpreviously separated by a different device. Alternatively, thedistraction device and support structure can be used to activelyseparate the layers of tissue and remain in place to support the layersof tissue in order to maintain such separation. Unless more specificallyset forth in the claims, as used herein, “distraction device” and“distraction device support structure” encompasses any and all of these.In addition, it should be noted that the references to “first” and“second” members or devices are for convenience in the writtendescription. They may be combined to provide a single distractionassembly or structure of selected distraction height, and the assemblyis not limited to only two “devices” or to only three “sleeves” or“members.” In keeping with the broader aspects of the present inventionthe specific number of “devices” or “sleeves” or “members” can be variedaccording to the intended usage or design considerations.

It should also be understood that various embodiments of the device,system and method of the present invention are illustrated for purposesof explanation in the treatment of vertebral compression fractures,height restoration of a diseased disc, vertebral fusion procedures,replacement of removed discs or vertebra, intervertebral disc nucleuscontainment or annulus fibrous repair. However, in its broader aspects,the various features of the present invention are not limited to theseparticular applications and may be used in connection with other tissuelayers, such as soft tissue layers, although it has particular utilityand benefit in treatment of vertebral conditions within intervertebraldiscs or within vertebra themselves.

Various features of the devices and methods of the present invention arefurther described in U.S. Provisional Patent Application 60/963,974 andits attached Exhibits A, B, C, D and E which were filed Jun. 22, 2007and are hereby incorporated herein by reference. Additionally, thedevices, systems and methods described herein are particularly usefulwith medical devices and procedures that involve tissue distraction, forexample, as described in the following co-owned patent applications:U.S. Provisional Applications Nos. (1) 60/708,691, filed Aug. 16, 2005;(2) 60/738,432, filed November 21, (3) 60/784,185, filed Mar. 21, 2006,(4) 60/886,838, filed Jan. 26, 2007, and (5) 60/890,868 filed Feb. 21,2007; and (1) U.S. patent application Ser. No. 11/464,782, (2) Ser. No.11/464,790, (3) Ser. No. 11/464,793, (4) Ser. No. 11/464,807, (5) Ser.No. 11/464,812, and (6) Ser. No. 11/464,815, all of which were filedAug. 15, 2006. Co-owned U.S. patent application Ser. No. 12/034,853,entitled “Devices For Treating The Spine” attorney docket no.0301-0015.01, and 61/030,287, entitled “Method of InterdigitatingFlowable Material With Bone Tissue” attorney docket no. 0301-0023, bothof which were filed on Feb. 21, 2008 also described the devices, systemsand methods described particularly useful with medical devices andprocedures described herein. All of the foregoing co-owned applicationsare hereby incorporated herein by reference.

Distraction Device Systems and Methods of Use

FIG. 1 illustrates one embodiment of a distraction device supportstructure, generally designated as 100, defined by a first elongatedmember 102. The elongated member 102 is preferably comprised ofelongated elements, such as a thread or ribbon, made of biocompatiblematerials that are suitable for long term implantation into human tissuewhere treatment is needed. The biocompatible materials may be calciumphosphate, tricalcium phosphate, hydroxyapatite, polyetheretherketones(PEEK), nylon, Nitinol (NiTi) or any other suitable biocompatiblematerial.

During deployment, the first elongated member 102 preferably has agenerally linear configuration for insertion into tissue or betweentissue layers. When deployed into or between tissue, the first elongatedmember 102 changes, preferably by flexing or bending, to a generallyless linear configuration to define a distraction device supportstructure. For example, in FIG. 1, the first elongated member 102 can bebent or configured to form or define the multi-tiered arrangement,scaffolding or platform of the coil or spring-like distraction devicesupport structure 100 having a vertical extent (e.g., the distancebetween the uppermost and lowermost surfaces of the structure). Thedistraction device support structure 100 can serve to actively separateor support (or both) opposed tissue layers.

The first distraction device or member, hereafter first elongatedmember, 102 preferably includes features that add flexibility to theelongated member to assist in bending or changing the configuration ofthe elongated member from a generally linear configuration to a lesslinear configuration and vice versa. For example, the first elongatedmember 102 may include teeth 104 and slots 106 that aid in relievingstress and add flexibility to the elongated member.

To form the support structure 100, the first elongated member 102 can beconfigured into a helical configuration with preferably a tight pitchthat has an essentially cylindrical configuration. As shown, each turnor winding 108 is wound on top of or below the previous winding 108 a toform a plurality of stacked windings or tiers with lithe or no spacingbetween each winding or tier.

In one embodiment, the first elongated member 102 can be comprised of ashape memory material that naturally has the configuration of thedistraction device support structure 100. To deploy a first elongatedmember 102 that is naturally shaped into the coil-like support structure100, the elongated member 102 is inserted between the tissue layers in agenerally linear configuration, typically through a cannula. Because ofits shape memory properties, the elongated member 102 transforms fromits generally linear configuration to its natural coil-likeconfiguration to define the distraction device support structure 100upon insertion between tissue layers.

In an alternative embodiment, the first elongated member 102 is madefrom a material that does not have shape memory properties or has veryweak shape memory properties and a guide member such as a guide wirehaving a pre-selected shape is employed to deploy the first elongatedmember 102 between tissue layers and to configure the first elongatedmember into the distraction device support structure 100. As will bediscussed in more detail below, when the first elongated member 102 isintended to be deployed by a use guide member, the first elongatedmember can include an aperture, such as aperture 110, shown in FIG. 1,extending along with the first elongated member for passage of a guidemember therethrough. The guide member is inserted between tissue layersand formed into a pre-selected shape. The first elongated member isadvanced along the pre-shaped guide member to form the distractiondevice support structure.

Preferably, the distraction device support structure 100 includes ordefines an innerspace or resident volume 112. As used herein, “residentvolume” refers generally to a structural characteristic of the supportstructure. The resident volume is a volume that is generally defined bythe distraction device support structure. The resident volume is notnecessarily a volume completely enclosed by the distraction devicesupport structure and can be any volume generally defined by theelongated member(s). This term does not necessarily mean that theresident volume is an open or void volume or cavity and does notpreclude a situation in which the resident volume is, at some point intime, filled with another material, such as bone filler, cement, bonegraft material, therapeutic drugs or the like. It also does not precludethe resident volume from containing undisturbed human tissue that islocated or remains within the resident volume during or after deploymentof the elongated member(s), as will be explained in more detail below.For example, if the distraction device is employed to separate adjoiningsoft tissue layers, such as subcutaneous fat and underlying muscletissue, the resident volume of the distraction device support structuremay be hollow or void of tissue after separation. On the other hand, ifinserted into a vertebra having cancellous bone tissue therein, theresident volume will contain undisturbed bone tissue and no void orcavity is formed by the elongated member(s).

The elongated member 102 may be used alone or in conjunction with anaugmenting elongated distraction member device, such as spacer 114, thatoperatively cooperates with the first elongated member 102 in order toaugment or increase the vertical extent of the distraction devicesupport structure 100, as illustrated in FIG. 2. The elongateddistraction or augmenting member 114, hereafter the augmenting elongatedmember is generally similar to the first elongated member 102 and isalso preferably comprised of a generally elongated member made from orcoated with biocompatible materials. In the embodiment illustrated inFIG. 2, the augmenting elongated member 114 operatively cooperates withthe first elongated member 102 so that the windings 116 of theaugmenting elongated member 114 are inserted between the windings 108 ofthe first elongated member 102 to increase the height of or otherwiseaugment vertical dimensional extent of the distraction device supportstructure 100 to engage and distract the facing tissue layers of thedisc or vertebra.

Preferably, the first and augmenting elongated members 102, 114 havecorresponding contoured surfaces that mechanically or frictionallycooperate or mate to assist in maintaining the positions of the firstand augmenting elongated members relative to each other and to increasethe stability of the support structure 100. For example, as illustratedin FIGS. 1, 2, 9, 10 and 11, the first elongated member 102 may have agenerally cross-like cross-sectional shape that includes a top surface118 and a bottom surface 120. The top surface 118 includes a protrusion122 substantially extending along the center of the top of the firstelongated member 102, and the bottom surface 120 includes a protrusion124 substantially extending along the center of the bottom of the firstelongated member 102. The augmenting elongated member 114 also includesa top contoured surface 126 and a bottom contoured surface 128. The topsurface 126 of the augmenting elongated member 114 includes an indent orgroove 130 that is configured to mate with the protrusion 124 of thebottom surface 120 of the first elongated member 102. The bottom surface128 of the augmenting elongated member 114 includes an indent or agroove 132 that is configured to mate with the protrusion 122 of the topsurface 118 of the first elongated member 102. The mating between theprotrusions 122, 124 and groves 130, 132 also can function as a guidetrack that guides the augmenting elongated member 114 between thewindings 108 of the first elongated member 102 as the augmentingelongated member is advanced between the windings 108 of the firstelongated member. Furthermore, the first and augmenting elongatedmembers 102, 114 could have additional mating surfaces extending fromeither side of the first and augmenting elongated member, which mate toprovide added stability to the support structure 100.

FIG. 3 through FIG. 8 illustrates the deployment of the first andaugmenting elongated members 102, 114 into a vertebral body 134. It willbe understood that the methods described herein of deploying the firstand augmenting elongated members into a vertebral body are forillustrative purposes and that the same or similar methods can be use todeploy the elongated members in other locations of the body, such as inan intervertebral disc or between other bone, skin or soft tissue.

Referring to FIG. 3, an access port 136 is made in the vertebral body134 using instruments and endoscopic procedures generally know to thoseskilled in the art or described in the above referenced co-owned patentapplications. A cannula 138 is then employed to advance a guide member140, such as the illustrated guide wire, through the access port 136 andinto the vertebral body 134. The guide member 140 is preferablycomprised of a shape memory material, such as Nitinol or other suitableshape memory material, such as a shape memory polymer, that has anatural or pre-set shape, for example, the illustrated coiledconfiguration. As the guide member 140 is advanced through the cannula138, the cannula constrains the guide member into a pre-deployedconfiguration, such as the illustrated generally elongated linearconfiguration, allowing an easy and minimally invasive deployment of theguide member into the treatment site. Because of the shape memoryproperties, the guide member 140 will return to its natural coil-shapeor deployed configuration once the constraint is removed, i.e., as theguide member exits the distal end portion 142 of the cannula 138 andenters the vertebral body 134. The guide member 140 can be advancedthrough the cannula 138 manually or with the aid of an advancingmechanism, such as the advancing mechanisms described in the abovereferenced co-owned applications.

The guide member 140 is advanced and deployed into cancellous bone ofthe vertebral body 134 until the distal end portion 143 of the guidemember 140 reaches the desired height or has the desired number of loopsor windings 144. Depending on the desired procedure, the guide member140 itself may function as a distraction device that contacts andseparates the endplates of a damaged vertebra or disc.

As illustrated in FIG. 4, the first elongated member 102 is insertedover the proximal end portion 145 of the guide member 140, and a pushermember (not shown) is placed over the guide member behind or proximalthe elongated member. The pusher member is employed to contact andadvance the first elongated member 102 forward or distally over theguide member 140 and out of the distal end portion 142 of the cannula138. As the first elongated member 102 is advanced forward (distally)over the guide member 140, the guide member guides the elongated memberout of the distal end portion 142 of the cannula 138 and into vertebralbody 134.

In the vertebral body 134, the first elongated member 102 follows alongthe coiled shaped distal end portion 143 of the guide member 140 andwinds into a coil shaped distraction device support structure 100 (FIG.5). The teeth 104 and slots 106 of the first elongated member 102enhance the flexibility of the device and assists in its ability tofollow the contour of the guide member. In this manner, the distal endportion of the guide member will define the shape of the first elongatedmember in situ, for instance in a vertebral body. With each formation ofan additional coil or windings 108 of the support structure 100, thesupport structure increases in height. At this point during theprocedure, the distraction device support structure formed by the firstelongated member may or may not function to distract tissue, dependingon the desired application. The support structure formed by the firstelongated member has a dimensional extent, a height in this example,that extends in a direction between the tissue layers (the endplates ofa single vertebra or opposed endplates of adjacent vertebra) to bedistracted. In the case of the spine, the direction would be generallyvertical when the patent is standing.

The first elongated member 102 is advanced over the guide member 140until the proximal end portion 148 of the first member 102 exits thedistal end portion 142 of the cannula 138 as illustrated in FIG. 6.While the guide member 140 retains the proximal end portion 148 of thefirst elongated member 102 in alignment with the distal end portion 142of the cannula 138, the augmenting elongated member 114 is advancedthrough the cannula 138 and positioned so that the contoured surfaces ofthe augmenting elongated member 114 align and mate with contouredsurfaces of the first elongated member 102, as discussed above.Alternatively, if the first and augmenting elongated members and thecannula are configured so that the first and augmenting elongatedmembers can both reside in the cannula at the same time and be advancedthrough the cannula simultaneously, the proximal end portion of thefirst elongated member can reside in the distal end portion of thecannula as the augmenting elongated member is deployed to augment thesupport structure.

As the augmenting elongated member 114 is advanced out of the cannula138, the augmenting member 114 is guided by the contoured surfacesbetween the windings 108 of the first elongated member 102. Theaugmenting member 114 can have a tapered or otherwise configured distalend portion 150 to aid in the insertion of the augmenting elongatedmember between the windings 108 of the first elongated member 102. Thewindings 116 of the augmenting elongated member are positioned betweenthe windings 108 of the first elongated member thereby augmenting orincreasing the height of the distraction device support structure 100,as illustrated in FIG. 7.

Referring to FIGS. 9, 10 and 11, as the augmenting elongated member 114is inserted between the windings of the first elongated member 102, thedimensional extent (in this case, the vertical dimension or the height)of the support structure 100 is increased by the height of H₁ for everyfull winding 116 of the augmenting elongated member 114 that is insertedbetween the windings 108 of the first elongated member 102. For example,in FIG. 9, the height of the support structure 100 is L₁ When onewinding 116 of the augmenting 114 is inserted between the windings 108of the first elongated member 102, as illustrated in FIG. 10, the heightof the support structure is L₁+H₁. Similarly, when a second winding 116of the augmenting elongated member 114 is inserted between the windings108 of the first elongated member 102, as shown in FIG. 11, the heightof the support structure 100 is L₁+H₁+H₁.

After a desired portion of the augmenting elongated member 114 isinserted between the windings 108 of the first elongated member 102 orthe augmenting elongated member is fully deployed, the guide member 140and the cannula 138 may be removed from the vertebral body 134 and thedistraction device support structure 100 distracts the superior andinferior endplates of the vertebral body, as illustrated in FIG. 8.After the support structure 100 has been implanted, bone filler, such asbone cement, bone graft, allograft, autograft, or the like, can beinserted in the resident volume 112 and/or around the support structureusing instruments and techniques generally known to those skilled in theart or generally disclosed in the above referenced co-owned patentapplications.

It should be recognized from the foregoing description that the use of asystem with two elongated members has several advantages. For example,one advantage of a two elongated member system is a potential reductionin the disturbance of tissue as the support structure is formed withinthe treatment area. In the two member system, the first elongated memberrequires less windings because the augmenting elongated member augmentsthe height of the support structure. Because the augmenting elongatedmember increases the height of the support structure, the height of thesupport structure increases without any further rotation of the firstelongated member. Less rotation of the first elongated memberpotentially results in a reduction in the disturbance of the tissuelocated in the treatment site.

Also, the use of a plurality of elongated members allows the supportstructure to be created through a single, relatively small aperture thatis significantly smaller than the structure created within the vertebraor disc. The resident volume also allows for the formation of a columnof bone tissue/bone cement amalgam that provides further support with avertebra.

The two elongated member system can have various alternative embodimentsand features without departing form the invention. For example, asillustrated in FIGS. 12, 13, 14 and 15, the mating surfaces of the firstand augmenting elongating members could have different configurations.In the embodiment of the distraction device support structure 151 shownin FIGS. 12 and 13, the first elongated member 152 includes a topsurface 154 and a bottom surface 156. The top surface 154 includes aconvex projection 158 extending along the top of the first elongatedmember 152, and the bottom surface 156 has a rounded or hemisphericalcross-sectional shape. The augmenting elongated member 160 includes atop surface 162 having the shape of a rounded groove extending along thetop of the augmenting elongated member. The top surface 162 of theaugmenting elongated member 160 is configured to mate with the bottomsurface 156 of the first elongated member 152. The bottom surface 164 ofthe augmenting elongated member 160 also includes a rounded groove 166extending along the augmenting elongated member. The rounded groove 166of the augmenting elongated member 160 is configured to mate with theconvex projection 158 extending from the top surface 154 of the firstelongated member 152. Similar to the previous embodiment, the mating ofthe contoured surfaces can function as a guide that guides theaugmenting elongated member 160 between the windings 168 of the firstelongated member 152 and can increase stability of the support structure151. Because of the curvature of the outer surfaces of the devices, asillustrated in FIG. 13, the first and augmenting elongated members alsocan be mated and advanced through the same rounded cannulasimultaneously, if desired.

In an alternative embodiment illustrated in FIGS. 14 and 15, thecontours of the top surface 170 and the bottom surface 174 of the firstelongated member 172 can be generally V-shaped or chevron shaped.Similarly, the contour of the top surface 176 and the bottom surface 180of the augmenting elongated member 178 also can be generally V-shaped orChevron shaped. When augmenting elongated member 178 is inserted betweenthe windings 182 of the first elongated member 172, the top surface 170of the first elongated member 172 mates with the bottom surface 180 ofthe augmenting elongated member 178, and the bottom surface 174 of thefirst elongated member 172 mates with the top surface 176 of theaugmenting elongated member 178 so that the windings 184 of theaugmenting elongated member 178 nest within the windings 182 of thefirst distractions device 172.

Furthermore, the top surface 176 of the augmenting elongated member 178can include a rounded projection 186 that mates with a correspondinggroove 188 located in the bottom surface 174 of the first elongatedmember 172 as best shown in FIG. 15. The engagement of the projection186 and the groove 188 can aid in guiding the augmenting elongatedmember 178 between the windings 182 of the first elongated member 172.

A further feature illustrated in the embodiment of the first elongatedmember 172 is that the elongated member includes stress relief region190 of any suitable shape, such as a region, void volume, region of moreflexible material or a lacking material. The stress relief region 190allow the elongated member to bow radially outwardly when axial pressureis placed on the support structure. Such stress relief regions increasethe compressibility and the elasticity of the support structure. Theseregions can be of any desired configuration and are preferably elongatedregions of substantially the same longitudinal extent as the elongatedmember itself.

It will be understood that this stress relief feature can be added toany of the elongated members disclosed herein. For example, FIGS. 14 and15 illustrate an embodiment of a elongated member having stress reliefregions 190. As an axial force, is placed on the top wall 170 of thedevice, the stress relief region translates the force to the sidewalls195 and 197 which bow outwardly. Such translation of stress can aidflexibility to the distraction device support structure and assist themaintaining the general shape of the distraction device supportstructure when such force is applied to the distraction device.

FIGS. 16-19 illustrate another embodiment of a elongated member systemthat includes a first elongated member 192 and a augmenting elongatedmember 194 that define a support structure 196.

Similar to the previous embodiments, the first elongated member 192comprises a generally elongated member that can be configured to form adistraction device support structure 196 having a dimensional, i.e.vertical, extent as illustrated in FIG. 20. Turning to FIGS. 16, 17 and19, the first elongated member 192 includes a top portion 198 and abottom portion 200 connected to each other by deformable sidewalls orwebs or connection members 206 spaced along each of the sidewalls. Thefirst elongated member 192 also may include a longitudinal passage 204extending generally longitudinally along the first member 192. Theconnection members 206 are biased to hold the upper portion 198 andlower portion 200 of the first elongated member 192 in a relativelytight or adjacent configuration of limited vertical dimensional extent.When the upper and lower portions 198, 200 of the first elongated member192 are in an adjacent configuration, the first elongated member 192 hasa first height of A₁ (FIG. 17).

Referring to FIGS. 16, 18 and 19, the augmenting elongated member 194 isan elongated member that can be inserted into and through a longitudinalpassage 204 (FIG. 17) extending along the first elongated member 192.The height B of the augmenting elongated member 194 can be generallylarger than that of the passage 204 of the first elongated member 192.However, the distal end portion 208 of the augmenting elongated member194 can be tapered to a size smaller than the passage 204 or otherwiseshaped to assist in the initial insertion of the augmenting elongatedmember 194 into the passageway 204 of the first elongated member 192.

Because the augmenting elongated member 194 has a height of B that isgreater than the height of the passage 204 of the first elongated member192, when the second elongated member 194 is inserted into the passage204 of the first elongated member 192, the augmenting elongated member194 contacts and forces the upper and lower portions 198, 200 of thefirst elongated member 192 apart, and the deformable sidewalls orconnection members 206 deform or stretch, to accommodate the separationof the upper and lower portions 198, 200. After the augmenting elongatedmember 194 has been inserted into the passage 204, the first and secondelongated members have a combined vertical dimensional extent or heightof A₂ (FIG. 19), which is larger than the height of A₁.

The deformable sidewalls or connection members 206 retain the upper andlower portions 198, 200 of the first elongated member 192 in a tight oradjacent configuration prior to insertion of the second elongated member194, and are sufficiently elastic or flexible to allow the upper andlower portions 198, 200 of the first elongated member 192 to separateinto a spaced apart configuration upon insertion of the augmentingelongated member 194.

Additionally, augmenting elongated member 194 should be sufficientlyrigid to keep the upper and lower portions 198, 200 of the firstelongated member 192 in a spaced apart relation. Yet, the augmentingelongated member 194 should also have sufficient lateral flexibility toallow it to transverse through the passage 204 of the first elongatedmember 192, which is curved when in situ as shown in FIG. 16. In otherwords, augmenting elongated member should be relatively rigid ornondeformable in a first direction that is generally parallel to thedirection of tissue separation and flexible in a plane generallyperpendicular to the direction of tissue separation.

In one embodiment, the augmenting elongated member 194 could includebarbs, tabs, or protrusions (not shown) spaced along the augmentingelongated member that function as anchors which retain the augmentingelongated member within the first elongated member. As the augmentingelongated member 194 is inserted into the passage 204 of the firstelongated member 192, the barbs contact the inside of the firstelongated member to prevent the augmenting elongated member from beingwithdrawn or retracted from the first elongated member. The barbs ortabs are preferably angled or otherwise configured to allow theaugmenting elongated member to be inserted into the first elongatedmember and to prevent the retraction or withdrawal of the augmentingelongated member from the first elongated member.

FIGS. 7, 8, 20 and 21 illustrate methods of deploying the two elongatedmember system of FIG. 16 within in a vertebral disc. It will beunderstood that the methods disclosed herein are for illustrativepurposes only and that the same or similar methods could be used todeploy the elongated members in vertebra as shown in FIGS. 3-6 or otherparts of the body.

Turning to FIG. 20, a guide member 210 (not shown) is deployed into avertebral body 212 using similar techniques as described above in regardto FIG. 3 with respect to member 143. Referring to FIG. 20, the guidemember 210 is inserted through an off set lumen 211 (FIGS. 16 and 17) ofthe first elongated member 192, and the first elongated member with theupper and lower portions 198, 200 in the tight adjacent configuration isadvanced along the guide member 210 through the cannula 214 and into thevertebral body 212. As the first elongated member 192 is advanced alongthe distal end portion of the guide member 210, the first elongatedmember 192 take the shape of the distal end portion of the guide memberand winds upon itself to form the distraction device support structure196 having an initial vertical dimensional extent in situ.

Referring to FIG. 21, after the distraction device support structure 196has been formed, the augmenting elongated member 194 is inserted throughthe cannula 214 and into the passage 204 of the first elongated member192 to augment the support structure 196. As the augmenting elongatedmember 194 is advanced into the passage 204 of the first elongatedmember 192, the deformable sidewalls 202 stretch or deform and the upperand lower portions 198, 200 move from their tight configuration to aspaced apart configuration, which increases the dimensional extent orheight of the structure formed by first elongated member 192. Theincrease in height of the first elongated member 192 in turn increasesthe height of the support structure 196, resulting in distraction of theendplates or further distraction of the endplates of the vertebra oneither side of the disc space. After the augmenting elongated member 194has been deployed, the cannula 214 and guide member 210 are preferablyremoved, leaving the support structure 196 implanted within thevertebral body 212.

Additional Distraction Device Systems and Methods of Use

One embodiment of a distraction device support structure defined by adistraction device 239 is shown in FIG. 22. The distraction device shownin FIG. 22 is comprised by a first elongated member 252, a secondelongated member 253 and an augmenting elongated member 255 thatcooperatively interacts with the first and second elongated members toincrease a dimensional aspect of the distraction device supportstructure. Keeping in mind that the distraction device may comprise twoor more separate members or sleeves, the distraction device ispreferably comprised of an elongated members, such as a thread orribbon, made of biocompatible materials (including metals and polymers)that are suitable for long term implantation into human tissue wheretreatment is needed. The biocompatible materials may, for example, becalcium phosphate, tricalcium phosphate, hydroxyapatite,polyetheretherketones (PEEK), nylon, Nitinol (NiTi) or any othersuitable biocompatible material.

Biocompatible material may also include PEEK with carbon fibers,polyethylenes of low, medium and or high densities, as well as nylonsand blends of materials that contain nylons.

During deployment, the elongated members which form the distractiondevice support structure preferably have a generally linearconfiguration for insertion into tissue or between tissue layers. Whendeployed into or between tissue, the elongated members changeconfiguration, preferably by flexing or bending, to a generally lesslinear configuration to define a distraction device support structure.For example, in FIG. 22, the elongated members 239 can be bent orotherwise configured to form or define a scaffolding, platform orstructure of a semicircular shape. In another embodiment shown in FIG.23, the distraction device 239 forms support structure having anannulus-like shape. The distraction device support structure can serveto actively separate and/or support (or both) opposed tissue layers suchas end plates of a vertebrae or opposed end plates of adjacentvertebrae.

The elongated members of the distraction device may include featuresthat add flexibility to the elongated member to assist in bending orchanging the configuration of the elongated member from a generallylinear configuration to a less linear configuration and vice versa. Forexample, the elongated member 252 seen in FIG. 24A may include lateralteeth 241 and intermediate slots or indents 242 that aid in relievingstress and add flexibility to the elongated member. When the elongatedmember is deployed in spinal tissue, the slots may also provide gaps forthe introduction of bone graft materials, cements, or pharmaceuticalcompounds to the spinal tissues.

In some embodiments, the elongated members may also be designed suchthat the adjacent teeth or other structures on either side of the slotprevent further bending beyond a finite desired angle. In FIG. 25,opposed sides of an elongated member 252 displays two different types ofstructures. Generally T-shaped members 237 on one side of the memberhave longitudinal extensions on their outmost edge such that adjacentmembers almost touch each other, leaving a relatively narrow opening atthe mouth the indent or aperture 238 between adjacent members. When theelongated member is bent toward the side having members 237, thelongitudinal extensions on adjacent members come in contact and provideresistance to further bending acting as a stop to limit furthercurvature. In contrast, the teeth or members 241 on the opposite side ofthe elongated member lack such longitudinal projections and thereforethe elongated member can be bent to a much greater degree in thisdirection before these teeth 241 come in contact with adjacent teeth tolimit further curvature. Also, it should be noted that by providing theT-shaped members 237 and intermediate indentations or gaps 238,increased flexibility is provided that allows the elongated member tobend toward the opposite side.

Additional features may be added to enhance or limit the flexibility ofthe elongated members of the distraction devices, including grooves,slots, channels, and pockets and teeth or other extensions or members ofvarious shapes. The slots, grooves, channels, and pockets may be placed,for example, in a linear pattern or spirally around the body of theelongated member. Through holes or apertures may also assist inproviding flexibility as well as serve as lumens for guide wires, orpull wires, discussed later. The placement of a greater number of thesefeatures in one region of an elongated member can make that region moreor less flexible than other regions of the device with fewer ordifferent flexibility enhancing or limiting features. In this mannerselect regions of the elongated member will be easier or more difficultto bend or deflect to assist the shaping of device in a desiredconformation. Alternatively, the flexibility features can be locateduniformly along a segment or the whole of the device to provide regionsof uniform flexibility.

Flexibility of first and second elongated members may also be providedby having a greater number of flexibility features on a particular sideor sides of the elongated members. For instance, a series of slots onone side of a member can reduce the amount of force required to deflectthat the elongated member toward or away from the slotted side.Flexibility of the elongated member may also be achieved or varied byfabricating the device from a combination of materials with differentdegrees of flexibility. For instance, by located more rigid material onone side of a member, the member may be easier to bend or deflect towardthat side. Particularly if the member is preformed into a desired curvedin situ configuration and temporarily straightened for insertion, themore rigid material may tend to retain the desired configuration to agreater degree than the other material and form the desiredconfiguration which introduced into the disc or vertebra. Also, theelongated member can have alternating or different sections along itslength that are made of different materials having different rigidity.

The presence of side teeth and slots on the elongated members has apotential added advantage. Contact between the teeth and tissue of thedisc or vertebra may help to anchor the member in position. For example,contact against the annular wall of the disc or vertebra to preventdevice movement in the circumferential direction after implantation.

In another embodiment of the present invention, the elongated membersare characterized by an ability to recover from temporary deformation.As noted previously, the elongated member(s) may be pre-set orpre-formed into a desired in situ shape and then temporarily reshaped,such as by straightening, for insertion. In this aspect, for instance, apre-shaped elongated member may tend to recover its shape more quicklyor completely in body-temperature spinal tissue after being in a lesscurved conformation during shipping and storage inside a deploymentcannula. In other embodiments, e.g., due to plastic creep or othermaterial characteristics, the elongated members may not recover theiroriginal shape after extended deformation in the cannula, and anexternal force may be used to shape the elongated member after it isinserted in the cannula. Such external force may be applied, forexample, by a guide member such as guide member 140 previously discussed(see FIGS. 3 and 4) or pull wires to be discussed in more detail later.

In some embodiments the deformation of elongated members are constrainedin a first axis and allowed in a plane at an angle to the first axis toallow deflection in a different plane. For instance, in FIG. 28 asemi-circular distraction device support structure is shown in avertebral disc. The support structure is formed by three elongatedmembers, 252, 253, and 255 and is relatively rigid in the direction(e.g., a vertical direction when standing) extending between two tissueslayers, i.e. the adjacent vertebra. The distraction device is resistantto deflection in a direction parallel to the longitudinal axis of thespine due to the relative solid, continuous structure of the elongatedmembers along this axis. Consequently, due to the structure of theelongated members 252, 253, 255 forming the distraction device supportstructure shown in FIG. 28, no deflection or only limited deflection isallowed in the direction of distraction. In contrast, the elongatedmembers are relatively more flexible in the plane perpendicular to thedirection of distraction to allow the elongated members to be shaped asdesired, such as curved or deflected to conform the shape of the spacein which they are implanted.

In certain embodiments the distraction device support structure does notsubstantially compress under vertical forces the human spine normallyendures, such as but not limited to up to about 1000 N. As describedearlier this relative rigidity may be provided by the elongated membershaving a nearly continuous or relatively solid core portion extendingalong the vertical extent of the structure. For instance, referring toFIG. 24A, an elongated member composed of PEEK with a center core orwall 236, between indents, that is from about 0.5 mm to about 1.7 mmwide will not substantially compress under normal physiological forces,and may even support a vertical force greater than about 3000 N. Moreparticularly the width of the core can be of any suitable size, such asfrom about 0.7 mm to about 1.5 mm, or from about 0.9 to about 1.3 mm, orfrom about 1 mm to about 1.2 mm and other ranges. The elongated memberas discussed previously can have teeth on both sides, with a centersolid core or, as shown in other embodiments, elongated members may haveteeth on only one side with a back or side wall providing a core supportfor vertical forces.

The distraction devices of the present invention may assume a variety ofshapes with a radius of curvature ranging from infinite, i.e. a straightline, to about 3 mm or less. Curved distraction devices may span arcsfrom about 30° to more than 360°. For flexibility, the depth of indents242 may vary, depending on the width 235 (FIG. 24A) of the elongatedmember at the teeth adjacent to the indent and the width of the coresupport between teeth 236. For instance, the width of elongated membersat their widest point can be, as an example only, from about 3 mm toabout 9 mm. More particularly for spinal application width maypreferably but not necessarily, be from about 5 mm to about 7 mm wide.As examples only, the depth of indents for an elongated member withteeth on only one side, a width 9 mm at the teeth, and a core support of1.5 mm could be about 7.5 mm (9 mm−1.5 mm=7.5 mm). For an elongatedmember having teeth on two opposed sides with indents of nearly equaldepth such as that shown in FIG. 24A, a width of 9 mm, and a coresupport of 1.5 mm, then the depth of indents on each side would be about3.75 mm. For an elongated member having different depth of indents onopposed sides such as those shown in FIG. 22, a width of 9 mm at theteeth and a core between teeth of 1.5 mm then the sum of the depth ofopposed indents would be 7.5 mm.

The width 234 of indents 242 may also affect the flexibility or degreeof flexing permitted. One example of the width to provide sufficientflexibility on the concave side of curved elongated member can be fromabout 0.5 mm to about 1.5 mm. More particularly width can be from about0.7 mm to about 1.3 mm, or from about 0.9 mm to about 1.1 mm. This maybe viewed as a desired or preferable minimum width, but other widths mayalso work depending on the procedure and size of the elongated memberand other features of such member.

In embodiments used to distract vertebral discs the height of thedistraction device support structure H_(d) in FIG. 33 preferably shouldbe sufficient to restore the disc to its normal height or thereabout,which will depend on the size of the patient and the discs location inthe spinal column. The height the support structure can be, for example,from about 5 mm to about 15 mm. More particularly the height can be fromabout 7.5 mm to about 13.5 mm, or about 9 mm to about 12 mm and rangestherein. For relatively short individuals or children, the disc size andconsequently the height of the support structure can be, for example,from about 5 mm to about 7 mm. For relatively tall individuals, the discheight and consequently the height of the support structure can be, forexample, from about 9 mm to about 15 mm or greater potentially.

As noted above, the shape of the disclosed distraction device supportstructures may be assisted, controlled and/or adjusted as the elongatedmembers are being deployed between the tissue to be distracted. Theforces required to control the shape of the disclosed elongated membersare compatible with typical hand-held delivery systems and tools. Forinstance, the shape of the elongated member may be controlled with pullwire systems deployed either inside the elongated member(s) and/oroutside the elongated member(s). The shape of the elongated members ofthe present invention may also be controlled with guide-wires such aspre-shaped nitinol wires, such as guidewire 140 described earlier. Thedisclosed elongated members may also be shaped with flexible or curvedscrews inserted into the elongated members. The disclosed elongatedmembers may also be shaped with flexible or curved rods in combinationwith a geometric pathway. The elongated members disclosed herein mayalso be pre-shaped such that the device returns to a shape that isidentical or similar to its original shape after being straightened orcurved to allow delivery to spinal or other tissues through a cannula.In some embodiments, the shape of the elongated members disclosed inthis invention may alter in response to a change in temperature orelectrical current, such that insertion into the tissue, e.g. spinaltissue, will result in the device assuming a more desired conformation.The various mechanisms disclosed herein for control of the shape ordeformation of elongated members of the present invention may be usedseparately or in combination such that more than one control mechanismmay be used to determine the shape and/or location of distraction devicesupport structure in situ.

The elongated members of the present invention may be manufactured usinga number of techniques including machining or milling techniques.Milling can include cutting elongated members from solid blocks or rodsof PEEK or other suitable material. Elongated members may also bemanufactured using molding techniques. Molding techniques includeco-molding various materials together to form a elongated member, aswell as molding a second material over a first material. Elongatedmembers may also be manufactured by injection molding or extrusionprocesses. In addition the elongated members of the present inventionmay be manufactured with Electrical Discharge machining process and byrapid prototyping methods including fused deposition modeling (FDM) andstereo lithography (SLA) techniques]

Elongated members manufactured from polymeric materials such as PEEK maybe pre-shaped by placing the elongated member in a metal fixture or jighaving a desired shape, such as a semicircular shape, and then heatingthe elongated member to relieve the bending stress. For instance theelongated member can be treated for about 5 minutes at about 160° C. Formany polymeric materials such as PEEK the pre-shaping process biases theelongated member toward a desired shape yet still allows the elongatedmember to be deformed either in the cannula or in situ after theelongated member is inserted into a tissue. In some embodiments, such aswhere the elongated members are comprised at least in part of PEEK, theelongated members do not shape memory material properties. Consequently,in some embodiments, particularly when PEEK is used, the elongatedmember does not return to its original shape without the additionalapplication of an external force to shape the member.

As discussed previously herein, the shape, distribution and size of theteeth 241 and slots 242 on the sides of the elongated members 239 can beconfigured to assist in forming various curved or bent shapes. Asillustrated in FIG. 23, the distraction device can be configured inclosed structures such as oval-, disc-, rounded corner quadrilateral-,and other rounded corner polygon-like distraction device supportstructures. Alternatively, the distraction device can be bent orconfigured in open structures such as semi-circular shapes in which theneither the proximal 243 nor the distal 244 end of the device touchanother end or other surface of the device.

The distal ends of the elongated members can have chamfer and wedgefeatures to ease the passage of the elongated member through tissue suchas bone or disc material. For example in FIG. 22, a chamfer feature 232is visible on the upper surface of the proximal end of first elongatedelement.

As illustrated in FIG. 23, in embodiments of the device forming closedstructures (i.e. structures defining a complete annulus) the firstelongated member can be configured with surfaces 245, 246 that mate orotherwise engage to assist in maintaining the closed structure such asthe annulus shape illustrated in FIG. 23. FIG. 24B illustrates anexample of such mating surfaces, with a protrusion on one end 245 of theelongated member that fits into a notch like recess 246 on the elongatedmember. The notch recess 246 is an indentation configured to securelyreceive the protrusion and is generally shaped to match the shape of theprotrusion 245. For instance, a rectangular protrusion may be matchedwith a generally rectangular indentation, or a ball shaped protrusionmay be match with a semicircular indentation. A particular surface 247of the indentation may be tapered to assist the entry of the protrusioninto the indentation.

The distraction device 239 may itself be composed of two or moreelongated members, hereafter exemplarily referred to a first member anda second member. The first member may also be referred to as a topmember or sleeve 252 while the second member may also be referred to asa bottom member or sleeve 253 as shown in FIGS. 29, 30 and 31. In oneembodiment the protrusions and indentations of the mating surfaces ofthe first and second elongated members mirror each other.

Turning to FIG. 26, in one embodiment, a first distraction device 240comprised of a first elongated member 252 and second elongated member253 can be comprised of a shape memory material that naturally has theconfiguration of the distraction device support structure in situ. Forinstance, to deploy a first distraction device 240 that is naturallyshaped into a semicircular support structure, the elongated members areforced into a linear configuration, such as in a cannula 284, andinserted between the tissue layers in a generally linear configuration,typically through the cannula 284. Because of its shape memoryproperties, the elongated members transforms from a generally linearconfiguration to their natural semi-circular, or annular or coil-likeconfiguration to define the distraction device support structure uponinsertion between tissue layers. The shape memory material used inelongated members optionally includes materials that are shaped into aparticular configuration using an annealing process such disclosed inthe co-owned patent applications referenced herein.

As seen in FIG. 23, the distraction device support structure 240 mayinclude or define an innerspace or resident volume. As used herein,“resident volume” refers generally to a structural characteristic of thesupport structure. The resident volume is a volume that is generallydefined by the distraction device support structure. The resident volumeis not necessarily a volume completely enclosed by the distractiondevice support structure and can be any volume generally defined by thedistraction device. This term does not necessarily mean that theresident volume is an open or void volume or cavity and does notpreclude a situation in which the resident volume is, at some point intime, filled with another material, such as bone graft, cement,therapeutic drugs or the like. It also does not preclude the residentvolume from containing undisturbed human tissue that is located orremains within the resident volume during or after deployment of thedistraction device, as will be explained in more detail below. Forexample, if the distraction device is employed to separate adjoiningsoft tissue layers, such as subcutaneous fat and underlying muscletissue, the resident volume of the distraction device support structuremay be hollow or void of tissue after separation. On the other hand, ifinserted into a vertebra having cancellous bone tissue therein, theresident volume will contain undisturbed bone tissue, and no void orcavity is formed by the distraction device. Similarly, if inserted intoa spinal disc, the resident volume may contain undisturbed disc tissuesuch as a portion of the nucleus pulposus or bone graft material placedbefore or after installation.

As illustrated in FIGS. 27-29, the first distraction device, composed offirst and second elongated members, may be used alone or in conjunctionwith a second distraction device 255 or spacer hereafter exemplarilyreferred to as an augmenting elongated member that operativelycooperates with the first 252 and second 253 elongated members of thefirst distraction device in order to augment the distraction devicesupport structure. The augmenting elongated member 255 preferablycomprises a generally elongated member made from biocompatible materialsand as shown in FIGS. 30 and 33 may have any of various additionalfeatures or aspects such as teeth 241 and slots 242. In the embodimentillustrated in FIGS. 27 and 28, the augmenting elongated memberoperatively cooperates with the first and second elongated members suchthat the augmenting member 255 is inserted and slides between the firstelongated member 252 and the second elongated member 253 to increase theheight of or otherwise augment the distraction device support structure.The degree of height increase of or other augmentation of thedistraction device support structure is dependent upon the height (orwidth) of the augmenting elongated member. For instance, as illustratedin FIGS. 33 and 34 thicker augmenting elongated member 255 will cause agreater increase the height of the distraction device support structurethan a thinner augmenting elongated member. However, once augmented, theheight of the distraction device is fixed and is not adjustable orvariable. The augmenting member is preferably fixed in position betweenthe first and second elongated members and not removal.

In one embodiment the thickness of the augmenting elongated member 255can be different along its length to cause different amounts ofadditional distraction along the length of the distraction device. Forinstance, the proximal portion of the augmenting member may be thicker(taller) than the distal portion of the augmenting member, then theincrease of the height of the proximal portion of the first device willbe greater than the augmentation of height for the distal portion of thedevice. The ability to create a greater increase in height in one regionof a distraction device allows for adjustments in the curvature of thespine of a patient. For instance, a collapsed disc in the lumbar regionof the spine can result in the loss of the normal lordosis in the lumbarregion of the spine. The insertion of a augmenting elongated member 255of variable thickness in a distraction device installed in a collapsedlumbar disc can restore the lumbar disc to the more normal morphology ofa greater height on its anterior region as compared to its posteriorregion—in that situation, the augmenting member may have a greaterheight its central region between the distal and proximal ends than ateither the proximal end or distal end.

In addition to different thickness or height of the augmenting member,either or both of the first or second elongated member can also be madeto have different thickness at different locations, such as by alteringthe surfaces of the first and second elongated members to match thelordotic angle in the device final configuration. For example, if thedevice is to be deployed in a semi-circular configuration (see FIGS.45-46) with the middle of the length of the elongated members placed atthe most anterior portion of the disc space, the height of the proximaland distal ends of the first and second elongated members could betapered gradually down to match the desired lordotic angle. In additionto such tapering, a single or multiple thin/small profile protrusion(s)matching the normal max device profile running along the length can beleft on the tapered upper or lower faces of the first and secondelongated members. These protrusions may act to stabilize the first andsecond elongated members inside the cannula during deployment, but onceimplanted inside the disc space, the thin/small profile protrusionswould preferentially subside until the tapered outer surfaces of thefirst and second elongated members are supporting the lordotic face ofthe endplates.

The first 240 and second 255 elongated members may have correspondingcontoured surfaces or features that mechanically or frictionallyco-operate or mate to assist in maintaining the positions of the firstand second elongated members relative to each other and to increase thestability of the support structure. As noted earlier, it should be notedthat the references to “first” and “second” distraction devices is forconvenience in the written description. They are combined to provide asingle distraction assembly or structure of selected distraction height,and the assembly is not limited to only two “devices” or to only three“sleeves” or “members.” In keeping with the broader aspects of thepresent invention the specific number of “devices” or “sleeves” or“members” can be varied according to the intended usage or designconsiderations.

As illustrated in FIGS. 29, 30 and 31 the first distraction device has afirst elongated member 252 that includes a top surface 256 and secondelongated member 253 that includes a bottom surface 258. To increasetraction against tissue and reduce the chances for slippage or movement,the top surface of the first elongated member 256 may includetissue-engaging structures, such as intermittent, spaced apartprotrusions 266 including ribs, teeth or textured surface or the likeand the bottom surface of the second elongated member 258 may alsoinclude similar protrusions 267. In some embodiments an individualprotrusion may extend substantially along the top surface 256 of thefirst elongated member, and an individual protrusion may extendsubstantially along the bottom surface 258 of the second elongatedmember. In other embodiments as shown in FIGS. 22 and 36 an individualprotrusion may be elongated bars that extend laterally along the topsurface of first elongated member and the bottom surface of the secondelongated member.

The bottom surface 257 of the first elongated member 252 240 may containa contoured surface 262, while the top side 259 of the second elongatedmember 253 240 may also be contoured 263, as shown in FIGS. 31, 32, 33,and 33. The augmenting elongated 255 member also may include a topcontoured surface 265 or and a bottom contoured surface 266. Asillustrated in FIGS. 32 and 33, the top surface 264 of the augmentingelongated member may include a protrusion raised or rib 265 that isconfigured to mate with an indentation or slot 262 in the bottom of thefirst elongated member 252. Alternatively, the top surface of theaugmenting elongated member may include an indentation or that isconfigured to mate with a protrusion or rib on the bottom surface of thefirst elongated member. As illustrated in FIGS. 33 and 34, the bottomsurface 266 of the augmenting elongated member may include a protrusion267 or a groove 268 that is configured to mate with a groove 263 or aprotrusion 269 included in the top surface 259 of the second elongatedmember of the first distraction device 240.

As shown in FIGS. 33, and 34, the cooperation between the protrusionsand grooves in the interfacing surfaces between of the elongated membersalso can function as a guide or guide track that directs the augmentingelongated member 255 between the first 252 and second 253 elongatedmembers. As seen in FIGS. 29, 30 and 36, the entrances to grooves 262,263 of the first and second elongated members can also be ramped 274 toprovide a larger opening on the proximal ends of the grooves to ease theentry of a tapered 273 distal end of augmenting 255 member between thefirst and second elongated members. Furthermore, the elongated membersmay have additional mating or guiding surfaces extending from eithersides of elongated members which provide added stability to theresulting support structure.

In an embodiment illustrated in FIG. 49, the first elongated member 252may have projections 270 along the bottom surface 257. Similarly, thetop surface 259 of the second elongated member 253 may also haveprojections 271. The projections 270, 271 on the bottom of the firstelongated member and the top of the second elongated member may beshaped to define internal threads or thread segments. The augmentingelongated member 555 may also have projections 272 along its externalsurface that are configured as external threads. The protrusions 272 onthe surface of the augmenting elongated member can cooperate with theprotrusions 270, 271 on the first and second elongated members to allowthreading advance of the augmenting member between the first and secondmembers. Threading the augmenting elongated member 255 between the first252 and second 253 elongated members can separate the first 252 andsecond elongated members 253 to augment the height of the distractionsupport structure. Using a threaded arrangement also provides amechanical advantage that may also assist in overcoming internalfriction and ease the insertion of the augmenting member between thefirst and second elongated members

As illustrated in FIGS. 29, 30, and 49, the distal end 273 of theaugmenting elongated member may have a smaller or taperedcross-sectional area that assists in initiating the insertion orthreading of the augmenting elongated member 255 between the first andsecond elongated members. As shown in FIG. 49, the proximal end 243 ofthe first and second elongated members of the may have an outwardlytapered regions 274 extending in from the proximal end 243 of the firstand second elongated members along the interface of the first 252 andsecond 253 elongated members. These outwardly tapered regions on theproximal ends of the first and second elongated members form an enlargedreceiving region that may assist in aligning the elongated members andin initiating the threading of the augmenting 255 elongated memberbetween the first 252 and second 253 elongated members.

For rotating the augmenting member 255 to thread it into position, theproximal end 276 (FIGS. 50-53) of the augmenting elongated member maycontain either a protrusion 277 or a recess 278 shaped to secure theinteraction of the augmenting elongated member with a torque deliverytool. A wide variety of shapes can be used to facilitate the interactionof the augmenting elongated member and the torque delivery device, forexample in FIGS. 50-53 Phillip's-, square-, and star-type endings areshown. These shapes are shown for illustrative purposed and the use ofother shapes (oval, diamond, triangle, hexagon, octagon, polygons etc,as well as sets of two or more protrusions or recesses) to secure theinteraction of the torque tool and the proximal end 276 of augmentingelongated member fall within the scope of this disclosure.

To insert the distraction assembly into an intervertebral disc, anaccess port is made through the annulus of a disc using instruments andendoscopic or minimally invasive procedures generally known to thoseskilled in the art or described in the above referenced co-owned patentapplications. Optionally all or a portion of nucleus pulposus is removedand the endplates of the adjacent vertebra are scraped to cause bleedingand promote the fusion of bone graft material to the vertebralendplates. Sizing paddles or like apparatus, may be slipped through theaccess port to determine the minimum disc height. A cannula 254 is thenemployed to advance a guide member, such as the illustrated deliverywire 279 of FIG. 47, through the access port and into the intervertebraldisc. The guide member 279 is preferably comprised of a shape memorymaterial, such as Nitinol or other suitable shape memory material, suchas a shape memory polymer, that has a natural or pre-set shape, forexample, the illustrated annulus or semicircular configuration. As theguide member is advanced through the cannula 254, the cannula constrainsthe guide member into a pre-deployed configuration, generally anelongated linear configuration, allowing an easy and minimally invasivedeployment of the guide member into the treatment site. Because of theshape memory properties, the guide member will return to its naturalcurved-shape or deployed configuration once the constraint is removed,i.e., as the distal end of the guide member 281 exits the distal endportion of the cannula 254 and enters the disc. The guide member 280 canbe advanced through the cannula 254 manually or with the aid of anadvancing mechanism, such as the advancing mechanisms described in theabove referenced co-owned applications.

The guide member 279 is advanced and deployed into the disc, typicallyalong the inner wall of the annulus fibrous, however, depending on thenature of the repair, other paths may be selected for the guide member.Advancement of the guide member 279 is halted when the guide memberforms the desired closed (e.g., rounded polygons and annular) or openstructure (e.g., semicircular) structure. Depending on the desiredprocedure, the guide member 279 itself may function as a distractiondevice, separating adjacent vertebrae. As illustrated in FIG. 47, forexample, the first and second elongated members 252 and 253 are insertedover the guide member 279. The first and second members may have facingsurfaces that cooperate with the augmenting member or with each other.Referring back to FIGS. 29-34 for examples of this, a slot or groove 262may be provided in the bottom of the first elongated member 252 and aslot or groove 263 the top of the second elongated member 259, and theguide member maybe configured to fit in one or both of these grooves. Inaddition as discussed herein, these grooves 262, 263 may also serve asguides for the insertion of the augmenting elongated member 255 betweenthe first and second elongated members 252, 253. Alternatively separateguidewire lumens 282 and 283 may be provided in the first and secondelongated members, and they may be inserted by passing them overseparate guidewires or members.

To advance the elongated member, as illustrated in FIGS. 35 and 37, apusher member, for example a plunger 297 can be placed over the guidemember behind or proximal to the elongated members. The pusher member isemployed to contact and advance the first members forward or distallyover the guide member and out of the distal end portion of the cannula.As the first member(s) are advanced forward (distally) over the guidemember, the guide member directs them out of the distal end portion ofthe cannula and into the intervertebral disc.

Turning back to FIG. 47, in the intervertebral disc, the pair of firstand second elongated members (sometimes referred to as the firstdistraction device 240) in FIGS. 29-41 and 47-48 follows along thedistal end portion 279 of the guide member and may be shaped by theguide member to form the desired open or closed (or other) shapeddistraction device support structure. Although not required, the teeth241 and slots 242 of the elongated members, as described earlier,enhance the flexibility of the device and assist in its ability tofollow the contour of the guide member 279.

As shown in FIG. 47, the first and second elongated members 252, 253 maybe advanced over the guide member 279 until the proximal end portion 243of the first and second elongated members exit the distal end portion ofthe cannula 284. While the guide member 279 retains the proximal endportion 243 of the first and second elongated members in alignment withthe distal end portion of the cannula 284, the augmenting elongatedmember 255 may be advanced over the guide member and through the cannula254 and positioned so that the distal end of the augmenting elongatedmember (which may be tapered or contoured) aligns and mates withproximal surfaces of the first and second elongated members 252, 253 asdiscussed herein. Alternatively, the first and second elongated members252 and 253 and augmenting elongated member 255 and the cannula 254 maybe configured so that the first and second elongated members andaugmenting elongated member can all reside in the cannula at the sametime, and then all three members may be advanced through the cannulasimultaneously, until the proximal end portion of the first and secondelongated members reside in the distal end portion of the cannula 284 asthe augmenting elongated member 255 is inserted between the first andsecond elongated members 252, 253. As illustrated in FIG. 35, the distalend of cannula 284 may have cutouts 285 to allow the cannula to restrainfirst and second elongated members in one direction, whilesimultaneously allowing augmentation of the height of the first device240 (i.e., the first and second elongated members) in a second dimensionwhen the augmenting elongated member 255 is inserted between the firstand second elongated members 252 and 253.

Returning to FIG. 47, as the augmenting elongated member 255 is advancedout of the cannula 254, the augmenting elongated member may be directedby a guide member 279. As seen in FIGS. 47 and 48, the augmenting membermay have a lumen 286 which allows the augmenting elongated member 255 tobe loaded on the same guide member 279 as the first and second elongatedmembers 252, 253. Advancing the augmenting member along the guide member279 directs it to a location between the first and second elongatedmembers. As previously discussed herein, the augmenting elongated membercan have a tapered or otherwise configured distal end portion to aid inthe insertion of the augmenting member between the first and secondelongated member 252, 253.

In yet another embodiment illustrated in FIGS. 54-60, the augmentingelongated member may be a comprised of a plurality of separate segments287 instead of being a continuous member. When comprised of separatesegments, the augmenting member readily follows and conforms to theshape of the first and second elongated members in situ. The segments ofthe augmenting elongated member may contain top and/or bottom contouredfeatures such as grooves or protrusions that allow the segments tointeract with or cooperate with protrusions or grooves in the facingsurfaces of first and second elongated members. As discussed previouslyherein and shown in FIG. 54, an augmenting elongated member comprised ofsegments 287 may contain a lumen 288 through each segment, which lumenis loaded over a guide member 279 to facilitate the insertion of thesegments 287 of the augmenting elongated member between the first 252and second 253 elongated members. The height of the segments 287comprising the augmenting elongated member can be different such thatdifferent regions of the resulting distraction structure providedifferent amounts of height augmentation. As noted above, this abilityto control the height of the various regions of the support structureallows the correction of abnormal curvature of the spine for instance byselectively increasing the height on a particular side of intervertebraldisc or a vertebral body.

Also, the facing surfaces to segments can be contoured to interact withthe adjacent segments of the augmenting elongated member. As illustratedin FIG. 54, for example, the segments may possess opposed concave andconvex adjacent surfaces such that a proximal 290 concave surface on onesegment contacts and cooperated with a convex distal 289 surface of theadjacent segment. For illustrative purposes, a few examples of segmentshapes which allow segment interaction are shown in FIGS. 55-60. Inaddition to sliding or pivoting contact, adjacent segments may also haveinterlocking features.

After a desired portion of the augmenting elongated member is insertedbetween the first and second elongated members, the resultingdistraction device support structure distracts the intervertebral disc.At that point, the introducing cannula and guide members, if any, mayalso be removed. After the support structure has been implanted, bonefiller, such as bone cement, allograph, autograph or the like, can beinserted in the resident volume and/or around the support structureusing instruments and techniques generally known to those skilled in theart or generally disclosed in the above referenced co-owned patentapplications. Alternatively, the bone filler can be inserted into thedisc space after measuring the disc space and before the introduction ofthe distraction structure.

In another embodiment the shape of the first and second elongatedmembers can be controlled during insertion, by applying a greater forceto one side of the elongated members than is applied to the other side.The application of unequal force can cause the elongated members tocurve in a particular direction. For example, FIGS. 39, 40, and 41 showa system with a pull wire 291 that passes through both the top 252 andbottom 253 elongated members. The pull wires 291 may pass through a wirelumen 282, 283 of each top and bottom elongated members like those shownin FIGS. 31 and 39 or, alternatively, through a wire channel or slotthat is not fully enclosed. Pull wire 291 may be a single wire ormultiple wires and may be of any flexible material that can be usedexert a force along the length of the elongated members 252, 253, 255and include steel, Nitinol, fiber both synthetic and natural, or thelike. In the examples shown in FIGS. 39, 40, and 41 the pull wire 291 ison the left side of the elongated members 252, 253 (as viewed from theproximal end) and an exertion of force, a pull on the wires, will causethe elongated members to curve to the left in the direction of the pull.Alternatively, systems in which a push, an extension force, appliedthrough a rigid pusher could be provided to a elongated members to causethe elongated members to curve in the opposite to the direction of forceapplication.

Systems such as those shown in FIGS. 39, 40, and 41 which include a pullwire or wires 591 that pass through both the first 252 and second 253elongated members also tend to prevent the first and second members fromseparating during deployment into the spinal tissue. The use of pullwires 291 (and particularly a single pull wire) in both members alsoallows pull force to be exerted to maintains the position of the first252 and second 253 elongated members together within or adjacent to thedistal end of the cannula 284 while the augmenting member 255, is beinginserted between the first 252 and second elongated member 253. In otherembodiments, a pull wire 291 may only pass through one of the first 252or second 253 elongated members to control the shape and placement ofthe first and second members. A pull wire 291 or wires may also be usedto control the shape and placement of the augmenting member, such asmember 255 in FIGS. 25-30, by passing the wire through a lumen thatextend longitudinally through the augmenting member.

Imaging techniques, including X-ray, allow real-time and near real-timemonitoring of the location and curvature of distraction devices duringsurgery and systems which apply an unequal force to the first and secondelongated members 252, 253 also allow fine control with visualconfirmation of the placement and the shape of the first and secondelongated members in the spinal tissue. After the first the first andsecond elongated members 252, 253 are placed in the desired location inthe spinal tissue and the augmenting member 255 is inserted in betweenthe first and second elongated members 252, 253 to augment distraction,pull wires 291 may be removed by releasing the ends of the wire or wiresand withdrawing from the elongated members.

Various devices may be used to apply tension to the pull wires forshaping elongated members. As shown in FIGS. 37 and 38, the forceexerted on pull wires 291 and similar devices for delivering a greaterforce to one side of elongated members may be controlled by a platform294 or arrangement that is associated with an advancing mechanism 295. Aforce delivery platform can comprise, for example, thumbknob 293associated with an advancing mechanism, the plunger body 295 of FIGS.99a and 99 b.

The force delivery platform may contain regions 296 designed to attachpull wires 291. Examples of wire attachment regions includeinvaginations, slots such as the ferrule nests 294 seen in FIG. 38, aswell as clamps, brackets, screws etc. As illustrated in FIG. 38, thethumbknob 293 may have threads 298 that interact with threads 299 on thepuller platform 294 such that rotating the thumbknob 293 will adjust thetension of the pull wire 291.

As illustrated, the force delivery platform 292 may interact with theadvancement mechanism 295, for example through a keyway 297 as shown inFIG. 38, such that rotation of the thumbknob 293 adjusts the tension onpull wires 291 but does not cause rotation inside the advancementmechanism 295, i.e. the plunger body of the embodiment shown in FIGS. 37and 38. In addition to thumbknobs 293, the tension on the pull wires291, or other devices for delivery of a greater force to one side ofelongated members may also be controlled by similar tensioning devicesthat are known to one of skill in the art, such as screw-drives,plungers, gear mechanisms and the like.

The use of pull wires has other advantages also. The insertion of theaugmenting elongated member between the first and second elongatedmembers can create a repulsive force that can push the first and secondelongated members away from both the cannula of a delivery device andthe augmenting member. The force exerted by pull members such as pullwires controlling member curvature, and the force of friction betweenthe surfaces of the first and second members and the surroundingtissues, such as the endplates of the vertebra above and below a disc,can also serve to resist this repulsive force.

In some applications the magnitude of the resisting forces may makeinsertion of the augmenting member increasingly difficult. For instance,in some embodiments the first and second elongated members do notcontact the vertebral plates until the augmenting member is deployed toincrease the height of the support structure. Increasing the force onthe pull wires that control the curvature of the members to overcome therepulsive force can, if too much force is exerted, increase thecurvature of the first and second elongated member. Increasing thecurvature of the first and second elongated members can hinder theability of the augmenting elongated member to translate along thegrooves and/or protrusions of the first and second members which form aguide tract for the insertion of the augmenting member. An excessiveincrease in the force on the pull wires can also cause excessive orundesired curvature of the first and second members.

In one embodiment, an anchoring or tethering system can be used to holdthe first and second elongated members aligned with the distal end ofdelivery cannula while the augmenting elongated member is insertedbetween these members. The tethering system can include an anchoring ortethering cable which attaches to the proximal end regions of the firstand second elongated members and to the proximal end region of adelivery device. The attachment can be a cable or line that provideslittle resistance to the deployment of first and second elongatedmembers, permitting the members to exit the distal end of cannula.However the length and tension of the anchor cables or tethers areadjustable to provide increased tension after the first and secondelongated members have exited the cannula. The tethers keep the firstand second elongated members in close proximity to the distal end of thecannula allowing the insertion of the augmenting elongated memberbetween the first and second elongated member without having to increasethe tension on the pull wires controlling the curvature of the members.

In the embodiment shown in FIGS. 43 and 44, for example, the tether canbe attached to the first and second elongated member by looping thetether to form an attachment or anchor loop(s) which engage with theproximal end regions of first and second elongated members. The freeends of the tether line can be attached to attachment points 323, 324 inattachment wells 327 and 328 located in the proximal end region of thedelivery device. The tether lines 320, 321 can pass inside the deliverydevice including through the delivery cannula of the delivery device.The attachment loops can associate with the elongated members 252, 253to attach the members to the deliver device by passing through holes inthe proximal end region of the elongated members or around engagingsurfaces on the elongated members. In other embodiments, the tetherlines may also associated with the elongated members by passing throughslots, pull-wire lumens or other like features. The tether lines mayalso associated with various protrusions, teeth, slots on the proximalend region of the elongated members. Additionally, the first and secondelongated members can be attached to the delivery device with a singletether line or loop or more than one tether line or loop.

The embodiment shown in FIG. 43 illustrates the use a single tether wireor line to form two attachment loops 320, 321 by passing the wire arounda tensioning pin 322 located on the proximal region of the deliverydevice with each end of the tether attached to separate fixing pinslocated in attachment wells 327, 328 at the proximal region of thedelivery device. After the augmenting member has been deployed betweenthe first and second members, the anchoring loops attaching theelongated members to the delivery device can be released, for instance,by accessing the wire through a channel 325 and cutting the wire. Withthe tension released, the fixing pins are readily released and one endof the wire can be pulled to remove the wire from the first and/orsecond elongated members. In other embodiments, the tension on theanchor wire may be relaxed after the augmenting elongated member isdeployed, without cutting the anchoring wire, to ease the release of anend of the wire and the removal of the wire from the elongated members.

In the embodiment shown in FIG. 43, the amount of slack in the anchorloops is regulated by regulating tension on the tensioning pin 322. Thetensioning pin 322 which is located on a sliding feature 330 to which atensioning spring 326 is attached. The spring 326 can exert moderatetension on the sliding feature 330 to provide a limited resistance andprevent slack in the anchoring loops 321, 320 while allowing theelongated members to move down and out of delivery cannula 320. When theelongated members have exited the cannula the sliding feature hits astop, increasing the resistance on the anchoring loops 320, 321 andretaining the elongated members in close proximity to the distal end ofthe delivery cannula. The tension on the tensioning 322 pin, which canregulate the slack in the anchor loops, may be controlled with a spring326 such as a constant force spring, or variable force springs,ratcheting mechanisms, winding spools, stretchable cables with a limitedfinal length and the like.

In some embodiments ends of tether lines can be directly attached to thetensioning pin or multiple tensioning pins. In alternative embodiments,tether lines can be attached directly to spool type or ratchet typesystems with or without drag adjustment features.

In another embodiment, free ends of tether line can be attached to asingle site on the proximal end region of a delivery device, forinstance the tensioning 322 pin or a fixing pin. Alternatively, the eachfree end may be affixed to separate sites on the proximal end region ofthe delivery device. Tether lines, wires or cables 320 may be attachedto the delivery device or elongated members by releasable mechanicalfeatures such as screws, clamps, crimps and ferrules and other likemeans. Cables or wires may also be attached by knotting, gluing orpinching the cable to the delivery device or in some cases the elongatedmember.

The anchor or tether wire or cable may consist of materials suitable forsterilization and compatible for temporary contact with animal,including human tissue. Metal anchor cables include stainless steel,nitinol, or other suitable metal wires. Nonmetal anchor cables includenatural fibers and polymeric fibers including polyethylene, ultra-highmolecular eight polyethylene (UHMWPE), Victrex, Pet, or similarmedical-grade polymers.

In some embodiments the tether line wire or cable may be wound on aspindle, with the spindle controlling the tension on the tether. Thespindle may also limit the total amount of line released to hold thedeployed elongated members at the desired location in close proximity tothe distal end 334 of the cannula. The tension in tether lines or cablesmay be controlled by other means such as springs, resilient means,sliding mechanisms, rotating mechanisms, moving mechanisms, pulleys,stretchable lines and the like.

In the embodiments shown in FIGS. 43 and 44 the delivery devices havinganchoring mechanisms such as those discussed herein also have pullmembers that control the curvature of the elongated members. The tensionon the pull wires can be controlled independently of the regulation ofthe anchoring mechanism. For instance thumb screws 329 or thumb knobs331 can control the tension on pull wires to regulate the curvature ofthe elongated members. The embodiment shown in FIG. 44 shows a fullyassembled support structure with the augmenting elongated member 255deployed between the first 252 and second 253 elongated members beingheld at the distal 334 end of the delivery device by anchor cables orwires with the curvature of the device controlled by pull wires, notvisible in this view shown in FIG. 44, but comparable to those describedabove.

Tether and anchor cable or wire systems are also compatible withdelivery device utilizing guide members, for example a guide wire, tocontrol the curvature of the elongated members. In a system utilizing aguide wire, the anchor cable system also will hold the first and secondelongated members near the distal end of the delivery cannula while theaugmenting member is being inserted between the elongated members orbetween the winding of a single elongated member. After the augmentingelongated member is deployed, the anchor or tether cable can be releasedand the delivery device removed.

To assist in placement and retention of the distraction structure, asshown in FIG. 61, the elongated members of the implant device, which areradiolucent (or radiotranslucent), are provided with radiopaque markers,so that the elongated members may be aligned in desired orientations byarranging the elongated members such that the radiopaque markers of eachelongated member are in a desired orientation relative to the radiopaquemarkers of the other members of the insert devices. The elongatedmembers of the implant device can be manufactured from radiolucentmaterials. Examples of radiolucent materials includepolyetheretherketone (PEEK) (a preferred material),polyetherketoneketone (PEKK), nylon and ultra high molecular weightpolyethylenes (UMPE). The radiopaque markers are produced from materialthat is visible with X-ray technology i.e. material that blocks X-raysand is biocompatible. Examples of materials suitable for radiopaquemarkers include gold, platinum, tantalum, or other biocompatibleradiopaque material.

An example of a system of radiopaque markers used to position theelongated members of an implant device in a desired position is shown inFIG. 61. In FIG. 61, the augmenting elongated member 255 is shown asdeployed between the upper or first elongated member 252 and the loweror second elongated member 253. The upper elongated member 252 has aproximal 304, an intermediate 303, and a distal 304 radiopaque marker.Similarly, the augmenting elongated member 255 has a proximal 307, anintermediate 306, and a distal 305 radiopaque marker. The secondelongated member 253 also has a proximal 310, intermediate 309, and adistal 308 radiopaque marker. In FIG. 61 each of the augmenting 255,first 252 and second 253 elongated members of the implant device isillustrated in the desired orientation relative to the other memberswhen corresponding radiopaque markers of each elongated members, i.e.the distal markers 304, 307, 310, the middle markers 303, 306, 309, andproximal 302, 305, 308, are aligned. For example in FIG. 61 when theelongated members 252, 253, 255 of the implant device are in theirdesired orientation and the device is observed in a lateral view theproximal 304, 307, 310 markers of the elongated members form a lineparallel to the caudal-cephalic axis of the body. Similarly, as shown inFIG. 61 the intermediate or middle markers 303, 306, 309 and distalmarkers 302, 305, 308 of the properly positioned elongated members 252,253, 255 form lines that are parallel to each other and parallel to thecaudal-cephalic axis of the body.

Other arrangements of radiopaque markers also could be utilized toindicate that the elongated members of an implantation device are in adesired orientation. For instance, the number, size, shape and spacingof radiopaque markers on each elongated member can be varied, with thenumber of markers varying from elongated members having as few as onemarker to as many as about 10 markers. Instead of the radiopaque markersof the augmenting elongated member 255 aligning with a correspondingmarker on the first 252 and/or second 253 elongated members(s), properrelative orientation of the elongated members may be indicated by amarker(s) of the augmenting elongated member aligning between twomarkers of a first and/or second elongated member(s).

Alternatively, proper relative orientation of the elongated members maybe indicated when the marker or markers on the augmenting elongatedmember fall a particular predetermined distance from a marker or markerson the first and/or second elongated members or wherein distinctlyshaped markers are aligned or adjacent. Also, the size and orientationof radiopaque markers can be varied to assist in determining therelative position of the first, 252, second 253, and augmenting 255elongated members of the implantation device. For example, in FIG. 61radiopaque markers could be of different size. For example, the proximalmarkers 304, 307, 310 of the elongated members 252, 253, 255 could eachbe the same size, for example 2 mm in diameter, while the middle markers303, 306, 309 of the elongated members 252, 253, 255 each a second size,for example 1 mm in diameter, and the distal markers 302, 305, 308 eacha third size, for example 0.5 mm in diameter. In this way, a radiopaquemarker can be identified by the size of its cross-sectional diameterwhen viewed from a lateral or anterior posterior view.

The length of markers can be varied as well to assist identifying aparticular marker, for instance in FIG. 61 the middle markers 303, 306,309 of the members 252, 255, 253, could be spaced from the surface ofelongated members in this way the markers have a detectable gap betweenthe corresponding middle markers 303, 306, 309 even when the markers arealigned. In contrast, the proximal 304, 307, 310 and distal 302, 305,308 markers could extend to surface so as to appear to be touching thecorresponding proximal or distal marker when the markers are aligned.The orientation of the radiopaque markers 302-310 in the elongatedmembers 352, 353, 355 can also be varied to assist in identifyingparticular markers. For instance, the cylinder markers such as thoseillustrated in FIG. 61 can be arranged so that a particular set ofmarkers for example the middle markers 303, 306, 309 are parallel to thelateral axis while the other markers are parallel to the caudal-cephalicaxis.

In some embodiments, the shapes of radiopaque markers can also be variedto assist in identifying particular markers. For example, the shapes maybe selected such that when viewed in cross-section in a lateral oranterior posterior view using fluoroscopic techniques, the markersappear as circles, triangle, squares, rectangle other polygons, or otheridentifiable shapes. Utilizing markers of distinctive shapes in knownregions of the elongated members allows the surgeon to readily determinethe position of each elongated member of the implant device relative tothe position of the other elongated members of the device.

In addition to relative alignment, radiopaque markers placed at knownlocations in the radiolucent elongated members of an implantation devicealso allows a surgeon to determine the shape and location of the implantdevice in the disc space. In FIG. 61, for example, the elongated membersof an implant device are transparent and the position and shape of theelongated members in the disc space is revealed by the positions of theproximal radiopaque markers 304, 307, 310, the middle or intermediateradiopaque markers 303, 306, 309, and the distal radiopaque markers 302,305, 308. As an example, in a lateral fluoroscopic view, when the middleor intermediate radiopaque markers 303, 306, 309 are at a more anteriorlocation than the distal markers 302, 305, 308 or the proximal markers304, 307, 310, it indicates that the structure is a curved orientationin situ. The radius of curvature of the implant device can be determinedin part by the anterior posterior view in which the distance between theproximal markers 304, 307, 310 and the distal markers 302, 305, 308 canbe determined, with a greater distance between these distal and proximalmarkers corresponding to a larger the radius of curvature for theinsertion device. Increasing the number of radiopaque markers dispersedalong the elongated members 252, 255, 253 of the insert device may allowmore detailed determinations of the location and shape of implantdevices in spinal tissue.

In other embodiments the elongated members 552, 553, 555 of the implantdevice may be made partially radiolucent by adding a filler to theradiolucent material used to synthesize the elongated members. Partiallyradiolucent elongated members allow detection of the position of theelongated members without the use of radiopaque markers, but as theelongated members are semi-radiopaque, the device does not completelyblock observation of adjacent spinal tissue such as the bony fusionbetween vertebral bodies that forms after a fusion procedure. Materialsuitable for use as a radiopaque filler includes BaSO₄ or BiO₃. Theweight ratio of radiopaque filler material added to the radiolucentmaterials to produce a partially radiolucent elongated member may beselected to provide the desired radiolucence, and may range, forexample, from about 2% to about 20%. In other embodiments, thepercentage of radiopaque filler material will range from about 4% toabout 18%, about 6% to about 16%, and about 8% to about 14%. In otherembodiments the percentage of radiopaque material will range from about2% to about 9%.

In some embodiments the first, second, and augmenting elongated members,252, 253, 255 of an implantation device may interact to form lockingmechanisms that interact to interlock the elongated members in a desiredorientation relative to the other elongated members of the device.Interlocking mechanisms may be formed by mechanical interfering surfaceson one or more elongated members 252, 253, 255 that lock to one or moreelongated members of the implantation device to prevent a elongatedmember from moving relative to one or more other elongated members ofthe implantation device. The locking mechanism may assist in preventingthe elongated members of implantation device from slipping relative toone another in response to the stresses a patient's normal movementsplace the implantation device.

One embodiment of a locking mechanism is shown in FIGS. 66 and 67. FIG.66 shows a second elongated member 253 with an interlocking recess 313into which a locking protrusion 314 from the augmenting member can enterto lock the augmenting member 255 into a desired orientation relative tothe second elongated member 253. Also a locking protrusion 314 on thetop surface 264 of the augmenting elongated member may interact with aninterlocking recess 313 in the bottom surface 257 of the first elongatedmember to lock the augmenting elongated member 255 into a desiredorientation relative to the first elongated member 252. When fullyengaged all three elongated members are substantially locked againstrelative movement.

The guiding of the locking protrusion 313 into a interlocking recess 313may be assisted by locating the interlocking recess along a groove ortrack 263 on an elongated member. As seen in FIGS. 62 and 63, forexample, a groove 263 in the upper surface 259 of a second elongatedmember 253 can act as a guide in which a long protrusion or ridge 267 onthe bottom surface 266 of a augmenting elongated member 266 slidesdistally to its in situ position between the upper or first 252 andlower or second elongated members 253. A locking protrusion 314 on theupper surface of the augmenting elongated member may be cylindrically orotherwise shaped and, as shown in FIG. 62, the diameter of the lockingprotrusion may be wider than the width of the longitudinal guideprotrusions 267, 265 on the bottom and top surfaces of the augmentingelongated member. As illustrated in FIG. 63, interlocking recesses 313are elongated slots 263 in the first and second elongated members. Inaddition as shown in FIG. 63, the diameter of the locking protrusion 314is larger than the narrowest entryway 316 into the interlocking recess313. Consequently, the locking protrusion 314 can slide into theinterlocking recess from a wide entryway 315 but is too wide to passthrough the narrow entryway, preventing over-advancing of the augmentingmember.

As illustrated the locking protrusion 314 which fits into theinterlocking recess 313 may be any suitable size or material, such as acylinder or pin made of a radiopaque material with a diameter rangingfrom about 0.25 mm to about 2 mm. As shown in FIGS. 66 and 67, thelocking protrusion 314 may extend beyond the upper and lower surfaces ofthe elongated member in which the locking protrusion 314 is mounted suchthat once the locking protrusion enters the interlocking recess 313, thelocking protrusion 314 extends into the recess 313 and resists themovement of the protrusion out of the recess 313.

Alternatively, the parts may be reversed, and the locking protrusions314 may be found on the bottom 253 and/or top 252 elongated members andthe interlocking recess(es) 313 may be found on the augmenting elongatedmember 255. Of course, other locking arrangements involving interferingsurfaces between the first, second and augmenting elongated members arealso suitable.

As illustrated in FIGS. 66 and 67, the lower surface 257 of the firstelongated member and the upper surface 259 of the second elongatedmember may have features such as ramps 275, tapers, or concaveindentations to ease the entry of the locking protrusion 214 into theinterlocking recess 313. The outer surface of the locking protrusion mayalso be tapered 317 such that one edge is higher than another edge toallow the locking protrusion 314 easily entry into the interlockingrecess 313 but resist the locking protrusion 614 from exiting theinterlocking recess 313 by sliding back in the opposite direction fromwhich the locking protrusion 314 entered the interlocking recess 313.The taper 317 of the locking protrusion 314 can also aid the entry intointerlocking recess 313.

The maintenance of the position of locking protrusion within theinterlocking recess 313 may be enhanced by the geometry of the lockingprotrusion. For example, FIG. 64 shows a locking protrusion 314 withslots 319 that extend into the protrusion along its top and bottomsurfaces. The slot 319 may be compressed as the locking protrusion 314is being pushed into the interlocking recess 313 to ease entry of thelocking protrusion into the interlocking recess 313. Subsequent to entryof the interlocking recess 313, the slotted locking protrusion 314 canexpand to result in a tighter fit of the protrusion in the recess tohelp prevent the locking protrusion from exiting the interlockingrecess. Other geometries of the locking protrusions may also assist boththe entry and retention of the locking protrusion into an interlockingrecess. For instance, FIG. 65 illustrates a locking protrusion 314 thatis rounded on one side 320 and flatter 321 on a second side. The roundedside 320 of the locking protrusion 314 may assist the entry of thelocking protrusion 314 into an interlocking recess 313, while the flat321 side can assist in keeping the locking protrusion 314 from slippingout of the interlocking recess 313.

In addition to generally cylindrical shapes, locking protrusions 314 andinterlocking recesses 313 can be a number of shapes that ease entry ofthe locking protrusion into the interlocking recess and subsequent toentry, these same geometries also resist disengagement of the lockingprotrusion 314 from the interlocking recess 313. Examples of suitablegeometries for locking mechanisms include arrow like shapes trapezoidalshapes and other shapes with narrower leading edges and wider trailingedges. In some embodiments an insertion device may have more than onelocking mechanisms. In some embodiments, the locking mechanisms whetherone or more are only engaged when each elongated member of the insertiondevice is in the preferred orientation relative to the other members.

To assist the surgeon in positioning the elongated members themechanical features of the locking device may be contain a radiopaquematerial. For instance the locking protrusion 314 may be a tantalum pinand the interlocking recess 313 may be lined with tantalum or anotherradiopaque material.

Miscellaneous Other Features

The various embodiments of the present invention may employ otherfeatures to enhance the distraction structure or its method of use. Forexample, the distal end portion of elongated members can include anangled or sloped first section that has a length that is equal to aboutthe length required for one revolution or to form one winding.

The elongated members of the present invention can also include surfacesthat frictionally or mechanically engage each other during and after theformation of the distraction device support structure. The frictionallyengaging surfaces can provide several benefits, such as eliminating orreducing movement between adjacent windings of the support structure,providing better rotational movement and transmission of torque duringdeployment and preventing unwinding or dilation of the windings underaxial loading. For example, the elongated members of a distractiondevice may have frictionally engaging surfaces, knurls, varyingthickness in peaks and valleys, and the like.

After the distraction device has been implanted and the distractiondevice support structure has been formed, the interlocking of theadjacent windings reduced the amount of unwinding or radial dilationthat can be caused by axial loading. For example, in some cases, if theadjacent windings are not interlocked, loading or force in the axialdirection may cause the top and bottom ends of the distraction devicesupport structure to dilate or unwind. The engagement between the knurlsof the top and bottom walls interlocks the adjacent windings, whichassists in reducing such dilation.

As discussed above, the elongated members of a distraction device caninclude teeth and slots or indents that assist in adding flexibility tothe distraction device. Specifically, the elongated members may includeteeth that extend at an angle from the back wall or a central spine ofthe elongated member, for example at angles between about 30 degrees toabout 90 degrees relative to the spine, with slots or indentstherebetween. Because the teeth are angled away from the tissue, theangled teeth slide smoothly past the tissue as the elongate member isinserted, and resist retraction or withdrawal of the distraction deviceonce it is deployed into tissue.

The elongated member of the present invention may include interlockingwindings or tiers to form the distraction device support structure. Forexample, the elongated members may include projections and recesses thatare configured to accept the projections when the elongated members areconfigured to form an interlocked support structure.

The elongated members may include at least one anchor extending from aback wall of an elongated member to contact and in some cases imbed intothe cancellous bone surrounding the support structure. When acompressive load is placed on the support structure in the axialdirection, the anchor bear a portion of the load, which aids in thesupport structure maintaining its position within the tissue. Anchoringprojections may also be on the surfaces of the elongated members ofdistraction devices used in vertebral discs for disc repair, replacementor vertebral fusion.

After the distraction device has been deployed to form the supportstructure, cement may be injected in and around the distraction devicesupport structure to add stability to the support structure. In otherembodiments, for example with a distraction device used to promote thefusion of adjacent vertebra a bone graft material, including allograft,autograft and the like may be injected in the regions in and/or aroundthe distraction device deployed in the disc space. This is illustratedin FIGS. 45 and 46. The embodiment shown in FIGS. 45 and 46 illustratesa flowable material 350 including bone graft material, cements and thelike being delivered with a cannula 351 through the same opening 352 inthe annulus fibrosus 351 which was used to insert a semicirculardistraction device 239. The distraction device is deployed in the discspace and is adjacent the annulus fibrosus 353. In FIG. 45, the flowablematerial is shown exiting the cannula 351 and entering the disc space,and FIG. 46 shows the same disc with the cannula 351 removed and thedisc space including the opening 352 to the annulus filled with theflowable material 350. The flowable material may be delivered by anymethod known in the art and more particularly equipment used to deliveryof flowable material can include the cannula used to insert thedistraction device, a specialized cannula, and/or various injectionequipment.

As discussed above, elongated members can be deployed into tissue orbetween tissue layers by advancing the elongated member over a guidemember. One method of deploying a elongated member involves incrementaldeployment of the guide member and one or more elongated members. Theincremental method can be used to deploy the elongated member intotissue or between tissue layers at any desired location within the bodyand is particularly useful in treating spinal tissue, such as vertebraeand intervertebral discs. For example, a portion of the guide member isadvanced out of the distal end portion of a cannula and into a treatmentsite. Next, the elongated member is advanced over the portion of theguide member. The guide member is then further advanced out of thecannula to extend portion of the guide member past the distal endportion of the elongated member, and the elongated member is thenfurther advanced over the guide member. The incremental deployment ofthe guide member and elongated member continues until the elongatedmember or members are fully deployed in the vertebral body. Suchincremental deployment aids in maintaining the shape of the guidemember, in preventing radial dilation of the guide member, and reducesthe amount of friction between the guide member and the tissue in whichit is inserted.

As further may be used in the present invention the distal end portionof the guide member can be configured to reduce the amount ofpenetration force required for insertion of the guide member. The guidemember can also have other alternative configurations that aid in theguide member's ability to traverse through tissue, including a rotaryadvance arrangement.

For example, the guide member can include an outer elongated member thathas a lumen therethrough. An inner or central elongated member extendsthrough the lumen and past the distal end portion of the outer elongatedmember. Both the outer elongated member and the inner elongated memberscan be made of a shape memory material that has a natural coil orspring-like shape. Alternatively, either the outer elongated member orthe inner elongated member can be made of a shape memory material.

The above miscellaneous features are described more fully in U.S.application Ser. No. 12/034,853, file on the same day herewith, entitled“Devices For Treating The Spine” under attorney docket no. 0301-0015.01,and is hereby incorporated by reference.

The present invention has potential application and benefit for bothnucleus containment and annulus repair when employed in intervertebraldiscs. When a spinal disc herniation occurs, the nucleus pulposus of thedisc may extrude or bulge through a tear in the annulus fibrous to theoutside of the disc. The device and methods of the present invention canbe used as a containment device for containing the nucleus of within thedisc and to prevent herniation or bulging of the nucleus through theannulus of the disc, as well as for nucleus replacement to replace adysfunctional nucleus and act as a mechanical support.

For instance, a cannula can be placed through an access port into a discand a guide member deployed through the cannula into the disc. Utilizinga distraction device with a helical support structure, the guide membercan form a coiled or spring-like shape within the disc. In embodimentsutilizing a distraction device with a generally annular supportstructure such as FIGS. 1-6, the guide member can form a generallyannular shape. The guide member is preferably sized and shaped to fitbetween the annulus and nucleus and substantially surrounds the discnucleus. The deployed barrier encircles the nucleus to contain thenucleus and prevent it from bulging or extruding through the annulus.

With respect to annulus repair, the normal intervertebral disc has anouter ligamentous ring called the annulus surrounding the nucleuspulposus. The annulus binds the adjacent vertebrae together and isconstituted of collagen fibers that are attached to the vertebrae andcross each other so that half of the individual fibers will tighten asthe vertebrae are rotated in either direction, thus resisting twistingor torsional motion.

Occasionally fissures may form rents through the annular wall. In theseinstances, the nucleus pulposus is urged outwardly from the subannularspace through a rent, often into the spinal column. Extruded nucleuspulposus can, and often does, mechanically press on the spinal cord orspinal nerve rootlet. This painful condition is clinically referred toas a ruptured or herniated disc.

The distraction devices of the present invention described herein alsocan be used for annulus repair. Instead of treating a herniated disc byenclosing the nucleus, the distraction device can be used to replace orstrengthen a damaged annulus. For instance, a guide member or pull wiresystem can be used to form first and second elongated members into asemicircle shape and deliver said members to the region between thenucleus and a rent in the annular wall. If desired an augmenting membercan then be inserted between the first and second elongated members toassist in containing the rent and maintaining the desired placement ofthe containment device.

FIGS. 69-75 illustrate alternative embodiments of distraction devicesembodying aspects of the present invention. As illustrated in FIG. 71,the distraction device includes first and second elongated members 252and 253 and augmenting elongated member 255. Preferably all threeelongated members are pre-assembled for insertion into a spinal disc,vertebra or between other tissue to be distracted. In the configurationshown in FIGS. 69 and 70, the first and second elongated members eachhave a series of spaced apart recesses 355 that are located to alignwith a similar recess 356 in the facing surface of the opposingelongated member. When the first and second elongated members are inadjacent face to face position, the facing recesses define a series ofcavities each of which has an inclined or tapered, conical-like wall357, 358 as best seen, for example, in FIG. 69.

The augmenting elongated member 255 includes a series of spaced apartaugmenting or separating members 359 which have a shape generallycomparable to the shape of the cavities defined by the facing recessesin the first and second elongated members. The spaced apart augmentingmembers 359 are joined to the next adjacent augmenting member by arelatively thin web of material 360.

In the pre-assembled condition, the elongated augmenting member 255 maybe located between the first and second elongated members 252, 253, withthe distracting or augmenting members 359 located within the cavitiesformed by the facing recesses 355, 356. This allows the combinedstructure of the first and second elongated members and the augmentingelongated member to have a relatively small profile or narrow profilefor insertion between the tissue layers to be distracted, such as forinsertion into a spinal disc or vertebra. More specifically, the widthor height of the combined three member profile is only slightly largerthan that of the first and second members alone in a facingrelationship. The combined profile is larger than the first and secondprofile only by the dimension of the thin web of material 360 thatconnects the spaced apart augmenting members 359 of the elongatedaugmenting member 255. This construction is best seen in FIG. 69 whichshows the assembled three member arrangement.

After insertion between the tissues to be distracted while in thepreassembled configuration shown, for example, in FIG. 69, and afterforming into the in situ configuration for tissue distraction, whetherthat be by natural bias of the material itself, or by assistance of aguide member or pull wire, the device can be formed into a distractedcondition, in which the upper and lower surfaces of the first and secondelongated members are spread apart. The distraction is caused byexerting a pulling force or tension on the center augmenting elongatedmember. By pulling the augmenting elongated member, the tapered surfacesof the augmenting elements are forced against the mating taperedsurfaces of the cavities formed by the facing recesses of the first andsecond members. This results in a spreading action exerted on the firstand second members, forcing them to a spread-apart position as shown,for example, in FIG. 71 where the first and second members 252 and 253are spread apart by a distance approximately equal to the width of theaugmenting members 355 located on the elongated augmenting member 255.In other word, the combined structure shown in FIG. 69 beforedistraction has a dimensional extent extending between the upper surfaceof the first member 252 and the lower surface of the second member 253.This dimensional extent would extend generally vertical when insertedinto the spine or, in other words, generally parallel to the axis of thespine. That vertical extent is enlarged substantially as may be seen inFIG. 71 when the augmenting member has been pulled or moved to thedistracted position shown there, spreading apart the upper surface offirst elongated member 252 and lower surface of second elongated member253.

FIGS. 72-76 illustrated an embodiment of the present invention based ona variation of the approach described in connection with FIGS. 69-71,with a somewhat different structure. More particularly the structure ofthe first and second elongated members and the augmenting elongatedmembers of FIGS. 72-76 define a series of teeth 360, 362, 366 and slots361, 363, 365 in the combined structure (as shown in FIG. 72 beforedistraction) that readily accommodates bending or forming by guidewires,guide member or other external force into a semi-circular configuration(see FIGS. 75 and 76).

As best seen in FIG. 72, each of the first and second elongated members252 and 253 has a series of alternating teeth and slots disposed alongone side of the alternating member. The teeth vary in the verticalextent in order to receive and cooperate with mating structuresassociated with augmenting elongated member, as will be seen more fullyin this description and in the drawings. Turning to FIG. 74, which is aperspective view of the elongated augmenting member, it may be seen thatthe elongated augmenting member includes a repeating series of threeelements or structures. The first structure 364 is a tapered member withinclined upper and lower surfaces forming a generally wedgedcross-sectional shape, extending from a relatively narrow leading edge367 to a wider, i.e., higher, trailing edge 368. A second structureelement 366 is spaced from structure element 364 by a slot 371. Aconnecting member 365 is located between members 364 and 366 of adjacentseries.

When the augmenting elongated members in the pre-insertion position(before insertion between tissue to be distracted), as shown in FIG. 72,it may be seen that the wedge shaped members 364 are located betweenfacing teeth 360, and 362 of the first and second members, each of whichhave an inclined surface which generally matches the inclined surfacesof the wedge shaped member. According, when tension or pulling force isapplied to the augmenting elongated member, the interaction between thetapered surfaces of the augmenting members 364 and the inclined surfacesof the teeth 369, 370 on the first and second elongated members forcesthe first and second elongated members apart, spreading them to theposition shown in FIG. 73, in which they are spread apart approximatelyby a distance equal to the width the trailing edge 369 of member 364.Because the series of wedged shaped members and other members on theaugmenting elongated member are separated by slots, flexibility isenhanced and the structure created between the tissues is allowed to anassumed and retain a curved configuration, such as shown for example inFIGS. 75 and 76.

Turning to FIGS. 75 and 76, FIG. 75 illustrates the combined structureas it may be formed using, for example, a pull wire arrangement throughapertures 282 and 283, into a semi-circular configuration betweentissues to be distracted. The vertical extent between the upper surfaceof first elongated member 252 and lower surface of second elongatedmember 253 is not substantially greater with the augmenting elongatedmember in place between them in the pre-insertion position than it wouldbe without the elongated member in place, providing a low profile forinsertion of the combined structure of all three elongated membersbetween the tissue to be distracted. After insertion of the combinedstructure, tension applied to pull wires, may readily form the structureinto the semi-circular configuration as shown in FIG. 75. Because theadjoining elements of the first and second elongated members and theaugmenting elongated member form a series of spaced apart teeth withsubstantial slots therebetween, as best seen in FIG. 75, the combinedstructure is readily, formable or bendable by guidewire tension into theconfiguration shown in FIG. 75. In some embodiments, combined structurecan be substantially non-flexible along the length of the structure. Forexample as shown FIGS. 77 and 78, the structure can substantially solid,i.e. it may lack flexibility features such as the slots 361, 363, 365between the teeth 360, 362, 366 of FIGS. 72-76. In Such an embodimentthe combined structure is inserted into the disc and maintains thegenerally linear configuration shown in FIGS. 77 and 78, i.e. thecombined structure is not curved in situ. Preferably the combinedstructure is implanted within the disc so that it extends diagonallyacross the disc space.

At that point in the procedure, tension may be applied to augmentingelongated member, with the wedge shaped members engaging opposing teethof the first and second elongate members forcing the first and secondelongated members apart to the distracted position as shown for examplein FIG. 76, where the first and second elongated members are supportedin the distracted position by the elements of the augmenting elongatedmember. While this result may be achieved by other structures as well,it may be seen that the assemblies shown in FIGS. 69-76 provide for acombined first, second and augmenting elongating member structure ofrelatively low profile for insertion between the tissue layers to bedistracted, which structure may then be distracted or expanded to thedistracted position, having a larger a larger dimensional extent, orlarger vertical spacing, to provide the desired amount of distraction orsupport for the distracted tissue in situ.

Finally, turning to specific description of the use of pull wires in thedelivery of a distraction device, in accordance with another aspect ofthe present invention, the distraction device may be delivered by firstcreating a small access hole through the disc annulus and some or all ofthe nucleus pulposus is removed. In addition, the endplates of the twovertebra bordering the disc can be scraped to produce sufficientbleeding to promote the fusion of the vertebra to introduced bone graftmaterial.

A range of sizing paddles would be available with the delivery system.The physician slips in sizing paddles into the access hole and the discspace to check for the minimum disc height. The physician uses thepaddle in different access angles through the annulus openings to checkall areas of the disc. The minimum disc height is noted. Another largerversion of the sizing paddle may also be inserted at this point todetermine the desired final distracted height. Alternatively, a morecomplex tool, such as a minimally invasive expandable tool that measuresthe disc height and distraction force required to reach that height mayalso be used to find the minimum and final disc heights.

At this point, bone graft may be inserted into the disc space. Or it maybe used at a later step.

Based on the minimum and desired final disc height measurement from thesizing paddles, the physician chooses the distraction device size. Theouter cannula maximum outer dimension from the delivery system isideally similar or slightly smaller in height than the minimum discheight measured. Accounting for the cannula wall thickness and any gapbetween the outer cannula and the top to bottom height of the first andsecond elongated members, the first and second elongated memberstogether are slightly less in height, top to bottom, than the minimumdisc height.

Because the first and second elongated members together clear theminimum disc height, they can be pushed in easily using the main plungerin the delivery system. For delivery, the physician begins to push inthe first and second elongated members out of the outer cannula littleby little, for example by using a pusher or plunger. Between pushes, thephysician checks the curvature of the elongated members using X-ray. Bytensioning the puller wire, the physician adjusts the curvature of thetop and bottom members in real time to closely follow the inner wall ofthe disc annulus.

Once the entire length of the first and second elongated members are outof the outer cannula and within the disc, the proximal end of themembers are held to the leading edge of the cannula by the tension inthe puller wire. The physician makes a final adjustment to the pullerwire tension to set the final shape of the implant. The physician maydecide to make a full circle with the elongated members, or leave theimplant in a semi-circular shape.

The physician now loads the augmenting elongated member into thedelivery system (or it is pre-loaded prior to procedure inside the innercannula). The thickness or height of the augmenting elongated memberdetermines the amount of final distraction. Based on the dimensionalextent of the initial top and bottom (first and second) elongatedmembers, the physician chooses the augmenting elongated memberthickness. In this regard, the ultimate size of the assembly is fixedand not adjustable. It is anticipated that the augmenting elongatedmember, after insertion, cannot be withdrawn. Alternatively, the finaldistraction height of the combined structure may have been pre-selectedprior to implantation, based on disc height and distraction forcemeasurements taken in a prior step.

The physician then pushes the augmenting elongated member into the discspace. (In a combined structure as shown in FIGS. 69-76, he would pullthe augmenting elongated member.)

Being careful to hold the cannula immobile, the physician pushes theaugmenting elongated member until it makes contact with the back orproximal end of the first and second elongated members. The physicianchecks the alignment of all the elongated members and begins to push theaugmenting elongated member against the first and second elongatedmembers. The augmenting elongated member begins to wedge itself inbetween the first and second members. Depending on the thickness(height) of the augmenting elongated member, some slack may need to begiven at this point to the pull wire to allow further wedging.

Once the physician confirms that the tip of the augmenting elongatedmember is wedged securely and the interlocking slots of the threeelongated members are engaged, the augmenting elongated member isadvanced slowly while checking for changes in the curvature of theimplant. As before, the curvature can be adjusted in real time using thepull wire. The augmenting elongated member is pushed in all the wayuntil its back face is flush with the back faces of the first and secondmembers. The physician then makes a final check of the implant placementand desired distraction. If satisfied with implant placement and theamount of distraction, the physician unscrews the thumb knob at the backof the delivery system to access the ends of the pull wire(s) and clipsthe ferrule holding the wire(s). The physician then grasps the other endof the pull wire(s) and pulls on it carefully, withdrawing the entirepuller wire(s) out of the implant and out of the delivery system.

If bone graft is needed, it can be injected through the same deliverysystem and aimed into any gap between the two ends of the implant at theposterior side of the disc space. Alternatively the device deliverycannula may be removed from the disc, a separate bone-graft deliverycannula may be inserted into the disc and the bonegraft materialinjected. Finally, he physician withdraws the cannula from the annulusand performs repair, if needed, of the opening in the annulus. Althoughthe present invention has been described in terms of the preferred andillustrated embodiments, this is for the purpose of illustration and notlimitation. It is understood that the present invention is not limitedto the specific examples shown or discussed and is as set forth in theclaims as now or hereafter filed.

1-86. (canceled)
 87. A pre-assembled tissue distraction devicecomprising: an upper tissue-engaging member; a lower tissue-engagingmember; and an augmenting member at least partially positioned betweenthe upper and lower tissue-engaging members, wherein the pre-assembledtissue distraction device is configured to be inserted in a generallylinear configuration between adjacent tissue layers of a spine andarticulated from the generally linear configuration to a generally lesslinear configuration, and the augmenting member is operable while thepre-assembled tissue distraction device is in the generally less linearconfiguration to spread at least a portion of the upper and lowertissue-engaging members to place at least a portion of the uppertissue-engaging member into engagement with one of said adjacent tissuelayers of the spine and to place at least a portion of the lowertissue-engaging member into engagement with another one of said adjacenttissue layers of the spine.
 88. The pre-assembled tissue distractiondevice of claim 87, wherein the augmenting member is configured to bemanipulated by application of a force applied in a direction that isdifferent from a direction extending between the portions of thetissue-engaging members configured to engage said adjacent tissue layersof the spine.
 89. The pre-assembled tissue distraction device of claim87, wherein at least one of the upper and lower tissue-engaging membersincludes an inclined surface, and at least a portion of the augmentingmember has a wedge shape configured to engage the inclined surface tospread said at least a portion of the upper and lower tissue-engagingmembers.
 90. The pre-assembled tissue distraction device of claim 87,wherein each of the upper and lower tissue-engaging members includes aninclined surface, and at least a portion of the augmenting member has awedge shape configured to engage the inclined surfaces to spread said atleast a portion of the upper and lower tissue-engaging members.
 91. Thepre-assembled tissue distraction device of claim 87, wherein theaugmenting member extends between proximal and distal ends and isoperable to spread said at least a portion of the upper and lowertissue-engaging members by application of a force to one of the ends.92. A method of distracting adjacent tissue layers of a spine,comprising: providing a pre-assembled distraction device including anupper tissue-engaging member, a lower tissue-engaging member, and anaugmenting member at least partially positioned between the upper andlower tissue-engaging members; inserting the pre-assembled distractiondevice in a generally linear configuration between adjacent tissuelayers of a spine; articulating the pre-assembled distraction devicefrom the generally linear configuration to a generally less linearconfiguration; and operating the augmenting member while thepre-assembled distraction device is in the generally less linearconfiguration to spread at least a portion of the upper and lowertissue-engaging members to place at least a portion of the uppertissue-engaging member into engagement with one of said adjacent tissuelayers of the spine and to place at least a portion of the lowertissue-engaging member into engagement with another one of said adjacenttissue layers of the spine.
 93. The method of claim 92, wherein saidoperating the augmenting member includes applying a force to theaugmenting member in a direction that is different from a directionextending between the portions of the tissue-engaging members placedinto engagement with said adjacent tissue layers of the spine.
 94. Themethod of claim 92, wherein at least one of the upper and lowertissue-engaging members includes an inclined surface, at least a portionof the augmenting member has a wedge shape, and said operating theaugmenting member includes moving the wedge shape portion of theaugmenting member into engagement with the inclined surface to spreadsaid at least a portion of the upper and lower tissue-engaging members.95. The method of claim 92, wherein each of the upper and lowertissue-engaging members includes an inclined surface, at least a portionof the augmenting member has a wedge shape, and said operating theaugmenting member includes moving the wedge shape portion of theaugmenting member into engagement with the inclined surfaces to spreadsaid at least a portion of the upper and lower tissue-engaging members.96. The method of claim 92, wherein the augmenting member extendsbetween proximal and distal ends, and said operating the augmentingmember includes applying a force to one of the ends.
 97. A tissuedistraction device comprising: first and second elongated membersinsertable between adjacent tissue layers of a spine; an augmentingelongated member at least partially positionable in a selected positionbetween and in contact with the first and second elongated members; andfirst and second radiopaque markers substantially aligned in a directionextending between the adjacent tissue layers of the spine when theaugmenting elongated member is in the selected position, wherein each ofthe first and second radiopaque markers is associated with a differentone of the elongated members.
 98. The tissue distraction device of claim97, wherein one of the radiopaque markers is associated with theaugmenting elongated member.
 99. The tissue distraction device of claim98, wherein the augmenting elongated member is movable with respect tothe first and second elongated members from a first position in whichthe radiopaque markers are not substantially aligned in said directionextending between the adjacent tissue layers of the spine to theselected position in which the radiopaque markers are substantiallyaligned in said direction extending between the adjacent tissue layersof the spine.
 100. The tissue distraction device of claim 97, whereinthe radiopaque markers have a substantially circular cross-sectionalshape.
 101. The tissue distraction device of claim 97, furthercomprising a third radiopaque marker, wherein each of the first, second,and third radiopaque markers is associated with a different one of theelongated members.
 102. The tissue distraction device of claim 97,wherein the first and second radiopaque markers are substantiallyidentical.
 103. The tissue distraction device of claim 97, wherein eachof the elongated members extends between proximal and distal ends, andthe radiopaque markers are positioned adjacent to the distal end of theassociated elongated member.
 104. The tissue distraction device of claim103, wherein at least one of the elongated members is associated withone of the radiopaque markers and with a proximal radiopaque markerpositioned adjacent to the proximal end of said at least one of theelongated members.
 105. The tissue distraction device of claim 97,wherein at least one of the elongated members is associated with one ofthe radiopaque markers and with a differently shaped additionalradiopaque marker.
 106. A method of distracting adjacent tissue layersof a spine, comprising: providing a first elongated member, a secondelongated member, and an augmenting member, with a first radiopaquemarker associated with one of the elongated members and a secondradiopaque marker associated with a different one of the elongatedmembers; inserting the first and second elongated members betweenadjacent tissue layers of a spine; and moving the augmenting elongatedmember from a first position to a selected position between and incontact with the first and second elongated members, wherein the firstand second radiopaque markers are substantially aligned in a directionextending between the adjacent tissue layers of the spine when theaugmenting elongated member is in the selected position.
 107. The methodof claim 106, wherein one of the radiopaque markers is associated withthe augmenting elongated member, and said moving the augmentingelongated member from the first position to the selected positionincludes moving the radiopaque marker associated with the augmentingelongated member into substantial alignment with the other radiopaquemarker in the direction extending between the adjacent tissue layers ofthe spine.
 108. The method of claim 106, wherein the radiopaque markershave a substantially circular cross-sectional shape.
 109. The method ofclaim 106, wherein said providing the first elongated member, the secondelongated member, and the augmenting elongated member includes providinga third radiopaque marker, with each of the radiopaque markers beingassociated with a different one of the elongated members.
 110. Themethod of claim 106, wherein the first and second radiopaque markers aresubstantially identical.
 111. The method of claim 106, wherein each ofthe elongated members extends between proximal and distal ends, and theradiopaque markers are positioned adjacent to the distal end of theassociated elongated member.
 112. The method of claim 111, wherein atleast one of the elongated members is associated with one of theradiopaque markers and with a proximal radiopaque marker positionedadjacent to the proximal end of said at least one of the elongatedmembers.
 113. The method of claim 106, wherein at least one of theelongated members is associated with one of the radiopaque markers andwith a differently shaped additional radiopaque marker.